Articles By Tonya McKay

CurlChemist

18-mea layer

Advances in scientific characterization techniques have enabled us to obtain unprecedented levels of information about nanoscale materials due to the ability to both directly and indirectly observe these materials in situ (in their natural environment). Fortunately for us in the curly world, one complex biological system that has received study is human hair. Through use of new methods, scientists have been able to identify and study the role of the multitudes of subspecies and structures present in hair. This has provided us with new insight regarding the cuticle-cuticle cell membrane complex (CCMC), and its major lipid component, 18-methyl eicosanoic acid (18-MEA). We have found that this relatively small fatty acid plays a very important role in the health and beauty of our hair, and it is becoming a bit of a buzzword in the industry. What exactly is 18-MEA, and how does it make such an important contribution? Perhaps more importantly, how can we protect the 18-MEA levels in our hair or replenish it if we have depleted it?

Cuticle glue and cushion

The protective cuticle layer that encapsulates the outer portion of each hair strand is a highly complex biocomposite structure made up of multiple layers of overlapping protein scales. Between each layer of scales, there exists a region called the cuticle-cuticle cell membrane complex, which is comprised of several layers of both delta and beta protein structures, a significant amount of 18-MEA covalently bonded to the b-protein structure, and a small amount of unbound lipids such as oleic and palmitic acid. This entire structure acts as a protective cushion and cement between the cuticle scale layers.

The covalently-bonded 18-MEA is responsible for providing hair with its hydrophobicity (water-repellent property), which protects hair by preventing it from absorbing too much water from the environment. It also provides hair with softness, lubricity, and shine. More significantly, an intact layer of 18-MEA acts to decrease tangling in wet hair and in the transition from wet to dry, by encouraging adjacent hair strands to lie neatly in parallel to one another, smoothly aligned. It does this due to its ability to decrease surface friction by changing the receding contact angle of water. When hair is lacking 18-MEA, the strands become entangled and stuck to one another, and the hair dries more quickly in these tangled packets, resulting in greater tangling when hair is dry.

18-mea layer

Damage to the 18-MEA layer

18-MEA is not soluble in water and does not dissolve in most organic solvents, and since it is covalently bound, it is not easily removed via mechanical means. However, it is highly susceptible to alkaline hydrolysis and subsequent loss through rinsing, meaning that products and processes that use a higher pH possess the risk of destruction of your hair’s protective lipid layer. Loss of the protective 18-MEA layer renders hair hydrophilic, so that it absorbs too much water from the environment, which leads to frizz and physical damage to the hair due to swelling and breaking of structures. Hair lacking its lipid layer is also more prone to tangling, frizz, breakage, and loss of curl structure.

Some shampoos that have a higher pH, most soaps, and baking soda rinses can gradually deplete the 18-MEA layer in a cumulative fashion with each additional use. However, highly alkaline processes such as perm, relaxers, and synthetic dyes can cause sudden catastrophic depletion of the 18-MEA layer. For this reason, chemically processed hair is especially vulnerable to damage due to moisture and tangling. Loss of this 18-MEA layer is probably the characteristic we are describing when we say processed hair is porous. It is also important to note that exposure to light, both visible and ultraviolet (UV), also gradually decrease the 18-MEA content in hair.

Minimizing exposure to alkaline environments is one way to protect the health of your hair. Cleansers that have pH≤ 6.0 are the safest for your hair. Reducing the frequency with which you color or process your hair will also help. Protecting your hair from light is another good way to reduce loss of 18-MEA and other types of damage to your hair.

Replenishing the 18-MEA layer?

It would seem logical that we could just replace the 18-MEA that is removed from the hair by redepositing it via a product. However, we cannot exactly duplicate the work of nature, because 18-MEA is covalently bound to the beta-protein structure of the CCM. Fortunately, several companies have found that modified versions of 18-MEA (quaternized or delivered in mixtures with cationic surfactants) will selectively deposit onto the surface of damaged hair and can restore its hydrophobicity, decrease tangling and combing friction, and increase shine. The effect was found to be cumulative with additional uses of the product. Undamaged hair is unchanged when treated with these mixtures, so this is specifically beneficial to those with color or perm-damaged hair.

If your hair is damaged due to the use of alkaline processes or higher pH cleansing methods, replacing some of the lost 18-MEA will go a long way toward making your hair feel and look healthier and shinier. However, this is relatively new technology, so it is still challenging to find products exploiting these materials. Trevor Sorbie has an entire line based upon the beneficial properties of 18-MEA, called the “18-MEA Lipid Shine™ Line.”Another product line that contains 18-MEA is Scientific Essentials “Simply Scientific Hair™ Products.”


Unfortunately, hair is not exempt from the physical changes that happen as you age -- it becomes drier, less lustrous, and for most of the population, gradual loss of pigment progresses from an occasional gray strand to a scattering of gray hairs throughout the scalp, culminating at some point into completely gray or white hair.

Usually, in a person’s thirties (or earlier, depending upon genetics or health factors), their melanocytes begin to slow down in their production of melanin. This typically occurs just in a few follicles and then gradually spreads throughout the scalp. Random hairs may become lighter and may not even be noticed, but eventually some begin to show as gray or white. This is much more noticeable in darker hair, so the perception is often that people with black hair go gray earlier, but that is probably not the case. As melanin particles disappear from the cortex, certain changes to the structure and properties of the hair can be expected. While people do experience their gray hair as being very similar to their pigmented hair, this is definitely not universally true. It is possible that those who had more highly pigmented hair to begin with (brunette, as opposed to blonde) will experience greater changes in the physical properties of their hair once those pigments are gone.

gray hair

How Hair Pigment Works

Specialized cells called melanocytes reside around the follicle from which hair grows. These cells manufacture melanin, a water insoluble biopolymer produced by the amino acid tyrosine, and they disperse it into the cortex of developing strands of hair as they emerge from the follicle. Melanin is the substance responsible for pigment in our skin and hair, and it comes in three forms. Eumelanin is responsible for brown and black hair, and pheomelanin yields red hues. Mixtures of the types of pigments, as well as the concentration and distribution of the melanin particles result in varying shades of hair color present in nature.

Melanin exists as granules that are dispersed throughout the cortex in human hair, amongst the proteins, water molecules, and fatty acids. These granules have differing geometry and distribution, depending upon which type they are. Eumelanin is generally evenly distributed throughout the cortex, has an oval shape, and has sharply defined edges. Pheomelanin is more randomly distributed in the cortex and also is more irregularly shaped, often having both an oval shaped end and a rod-like end. The presence of these particles in the cortex may contribute to some of the mechanical properties of the hair strand, such as elasticity and strength. Another important role of melanin is to act as a protectant from environmental damage by absorbing ultraviolet radiation. The structure of the polymer enables it to absorb UV energy and release it as heat via a photochemical process, thereby preventing it from attacking and damaging the protein structures of the hair.

Graying Hair

Once melanocytes are no longer manufacturing melanin, they die. Their absence sometimes causes the follicle to change shape slightly, which results in a slightly different shape for subsequent hairs that grow from that follicle. This is important, because the geometry of a hair strand is a significant contributing factor to the curl pattern, or lack thereof, for that hair. This explains why the texture of some gray hairs often varies significantly from the rest of the hair. This can certainly be perplexing and frustrating.

One notable feature of gray hair that can contribute to its having different properties from pigmented hair is the presence of a medulla. Most animal fur contains a central hollow core called the medulla, which provides insulation for the mammal. In contrast, this feature is generally missing in human hair, but sometimes appears in white strands. This presence of this hollow core may change the physical properties of the hair, making it more wiry and unruly.

An additional explanation for variations in the properties of white hair is found in the absence of melanin particles from the cortex. This changes the overall structure of the region, which may affect properties of the hair, such as curl pattern, elasticity, or strength. Also, the cuticle of gray hair strands is often tighter than pigmented hair, making it more difficult to process chemically as well. This is especially relevant when attempting to hide gray hair with color. Gray hair typically needs a longer processing time or a pre-treatment to open the cuticle to allow penetration of the artificial dyes.

Perhaps the most significant feature of white hair is its vulnerability to damage from the sun. The absence of its natural sunscreen, melanin, leaves hair highly susceptible to mechanical degradation from UV radiation. This can lead to broken hairs, split ends, frizz, excessive tangling, and cuticle damage. The surface of hair can even lose its natural hydrophobic protection and become hydrophilic, allowing far too much water to penetrate into the hair, causing irrevocable damage. White hair is also vulnerable to yellowing from the sun due to oxidation.

gray hair

Caring for Gray Hair

Gray and white hair behave differently from your pigmented hair. It may be curlier, straighter, or wirier than the hair of your youth. It is also drier, more delicate, and prone to breakage or yellowing. Despite your best efforts, it may also be resistant to coverage when chemical dye processes are attempted. Some of these changes may require you to manage your own expectations and learn how to work with the hand you have been dealt, but many of the challenges can be overcome by making some adjustments to your usual routine. Take charge of your gray hair by embracing its differences and nourishing it daily. Gray hair, dyed or not, can be healthy and beautiful!

  1. Condition, condition, condition. Your gray hair requires more moisture than your once youthful, delicate curly locks. Natural oils, honey or agave treatments, deep conditioning protein packs, as well as daily leave-in conditioners can all help optimize the health of these fragile strands.
  2. Apply color to gray or white hair first, and let it sit longer to ensure penetration of the dyes. Some salons recommend application of a peroxide solution to gray hair prior to coloring, in order to prepare the cuticle, but use caution as this could be more damaging to the hair.
  3. If your gray covers more than 35% of your scalp, consider using a clarifying shampoo or vinegar rinse about once a month so to remove mineral build up that can cause discoloration of your hair.
  4. Be mindful that heat can be more damaging to white hair. Minimize its exposure to extreme high temperatures found in many straightening processes particularly.
  5. Protect your hair from harmful UV rays! Wear a hat, swim cap, or scarf if you plan to spend a lot of time in the sun. Use conditioning and styling products that contain UV-absorbing ingredients, such as cinnamidopropyltrimonium chloride or octyl methoxy cinnamate, which have been found to significantly reduce the negative effects of the sun on the mechanical properties of the hair. In addition to maintaining the mechanical integrity of the hair, these have been found to reduce yellowing of white and gray hair.

PHOTO TORI LOCKLEAR

By now you've likely encountered the hair tutorial gone wrong that resulted in unassuming YouTuber Tori Locklear losing a full section of hair. The country gasped with her when she realized what high heat had done to her hair, and many of us thought twice before touching a flat iron or curling wand to our strands again.

Temperatures encountered during blow-drying, flat-iron straightening, and hot curling processes can be high enough to cause severe trauma to the hair. Results of this can include cracks in the cuticle layer, bubbles or voids in the cortex, frayed and split ends, chipped and ragged cuticles, faded color, diminished curl and increased frizz, as well as, in Tori's case, broken strands. If avoiding high heat styling methods is not an option, it is important to take precautions to prevent or minimize damage. There are a number of products on the market advertised as heat protectant sprays, lotions, and serums which claim to prevent or repair the detrimental effects of high temperatures on hair. Are these products effective, and if so, how do they work, and which ingredients are responsible for their performance?

Heat & Hair

Flat-irons, curling, irons, and blow driers all impose extreme thermal stresses upon hair strands. With temperatures exceeding the boiling point of water (100°C) and reaching as high as 200°C or more, damage can occur by several different mechanisms.

Dehydration

One heat-induced phenomenon responsible for damage to hair is loss of moisture. Water molecules inside the cortex, both free and bound to keratin proteins, provide critical support to the structure and properties of hair. Evaporation of these molecules due to application of heat can alter the internal protein structure and change the intermolecular interactions that govern the mechanical properties of individual hair strands. This can change curl patterns, cause frizz, and result in hair that is less bouncy and more prone to breakage. The tactile feels of the hair is less pleasant too, having a straw-like texture. This sort of damage is pretty common with routine blow-drying.

Rapid Water Loss

The extremely high temperatures encountered in flat-iron straightening or even straightening using a hair dryer and round brush create intense conditions that can cause water to rapidly boil or “flash” off from sites where it resides within the interior of the hair shaft. This rapid boiling can create voids in the hair structure that can be seen via microscopy and look like strings of bubbles within the strand. These can cause ruptures that burst through the cuticle, leaving gaping spots in the hair, which inevitably lead to split ends and breakage. Cracks can form in the cuticle as well, making the hair vulnerable to further moisture loss and breakage. This type of damage is both severe and completely irreparable.

Protein Damage

Hair strands are complex biomaterials that derive the bulk of their properties from the keratin protein structures in the cuticle and cortex. Thermal degradation from styling tools can occur via softening of the keratin, disruption of the three-dimensional structures due to water loss, and conformational changes in the protein. All of these changes can adversely affect the strength, elasticity, curl, shine, and texture of the hair.

Oxidation of pigment particles

High temperatures can also cause oxidation of pigments found in hair, both naturally occurring ones and artificial hair color. This fading is particularly pronounced in reds, auburns and lighter brunette shades.

MORE: After-Party Hair Repair: Treat That Heat Damage

Products that Protect

Heat protectants are products marketed with the claim that they prevent damage to hair from high temperature styling. Multiple studies have shown that these can be very effective in reducing, but not eliminating thermal trauma to hair. How do they work? The key ingredients in heat protectant products work in a few different ways.

Reduction of moisture loss

Since it is clearly very harmful for hair to lose its precious water molecules, one of the key tasks of a heat protectant is to both maximize and seal in moisture. Humectants such as panthenol, propylene glycol, and phytantriol are used to bind as much water as possible to the hair. Polymers, silicones, and some botanical oils are used to seal the water inside the cortex. They achieve this by coating and encapsulating the strand of hair in a film through which water cannot diffuse. Testing of both control samples and silicone-treated hair strands via thermogravimetric analysis (TGA) showed that silicone treatment significantly improved moisture retention.

Insulation from high temperatures

Silicones (especially amine-functional ones, such as amodimethicone,) some polyquats, and copolymers of acrylates are particularly effective at minimizing the damaging effects of heat styling due to their low thermal conductivity. When evenly distributed across the hair surface into a protective film, these materials act as insulators by reducing the transfer of heat from the styling tool to the hair strand. Data from thermal analysis (DSC- differential scanning calorimetry) confirmed that heat flow was reduced to hair samples treated with these types of materials.

Raw materials suppliers such as Dow Corning, Croda, and GE have also used scanning electron microscopy (SEM) and mechanical testing to evaluate the levels of protection from damage provided by various silicones and heat protectant polymers, and they found that crack formation, cuticle damage, void formation, and loss of strength and elasticity were all reduced when hair was treated with a heat protectant polymer.

What Can We Learn from Tori's Mistake

If you enjoy the results of occasionally flat-iron straightening or blow drying your hair, heat protectant products can make a real difference in how your hair handles those extreme conditions. However, it is important to note that while thermal protection products containing the right mix of humectants and insulating materials can help reduce damage, they cannot completely prevent it. This means that if heat styling is frequently used, cumulative damage will occur. The only way to fix that type of damage is to cut off all the affected length. So, if you prefer to wear your hair long, use heat rarely. Another thing to keep in mind is that some of the polymers and silicones used by these products to encapsulate the hair strand may be difficult to remove and have been known to cause hair to feel sticky or tacky with repeat use.

MORE: I Tried a Dominican Blowout


Where does it come from?

Among the many botanical based ingredients currently popular in hair care routines, amla is perhaps the one that seems the most mysterious, at least from a chemistry point of view.

Amla is derived from the fruit of the Indian gooseberry or Phyllanthus emblica L., a deciduous tree found in both the tropical and subtropical portions of the Indian and Southeastern Asian countries.

The lemon-sized fruit is greenish yellow with attractive vertical striations and has a bitter, sour, and sweet taste. While amla fruit is primarily composed of water, it also contains a variety of sugars, carbohydrates, protein, fiber, minerals, and contains very high amounts of ascorbic acid (vitamin C). For many centuries it has been prized by practitioners of Ayurvedic medicine as well as many other groups for its reportedly amazing medicinal attributes as well as for its beneficial properties for hair and skin.

What does it do?

Advocates who support topical use of amla for hair claim that it is has many uses:

  • cleansing agent
  • deep conditioning treatment
  • dandruff remedy
  • prevents graying of hair
  • darkens hair without use of dyes
  • imparts shine
  • improves hair growth

Too good to be true?

It certainly sounds too good to be true. What exactly is in the amla that is sold for domestic use? Does its composition and chemistry lend any credibility to the many bold claims?

Unless you are fortunate to have access to the fresh fruit, amla is generally available as either a powder or oil. The light brown powder is obtained by drying the entire fruit and grinding it into a powder. The amla oil is actually made by soaking the dried fruit in another oil such as coconut, sesame seed, and sometimes mineral oil. Some of the components of the dried fruit seep into the carrier oil, which is filtered to remove the bits of fruit prior to market. This means that most amla oil products being sold are actually more of a botanical infusion of amla in coconut, sesame, or mineral oil. Although it is possible to extract the fatty acids from the seeds of the amla fruit in the same manner as they are extracted from coconuts, avocados, shea nuts, and argan fruit, it has not been the traditional manner of using this fruit.

ELLAGIC ACID

Chemical make-up of the amla powder

Since the dried powder is made from the whole fruit, it contains all of the nutrients found in the amla, including the fatty acids from the seeds, glucose and the complex carbohydrates, vitamins, phytochemicals, protein, and minerals. The fatty acids found in the seeds are predominantly polyunsaturated ones (~63%), with the remainder being made up of 27% monounsaturated fatty acids and 9-10% medium to long chain saturated fatty acids. These molecules are generally too large and unwieldy to penetrate into the cortex of a hair strand, so they coat the outside of the hair and provide some slip and emollient properties.

Amla & Vitamin C

Amla powder also contains large amounts of vitamin C, which acts as an antioxidant and anti-inflammatory agent, and also may stimulate collagen growth in scalp tissue.

Vitamin C also has antimicrobial properties that can help fight dandruff and other infections of the scalp. The mildly acidifying properties of vitamin C may also enhance the strength and quality of the cuticle layer of the hair and add some shine. Too much vitamin C can be drying to the hair though, so this is probably a good reason to use this powder only occasionally.

Gallic & Ellagic Acid

Two other interesting components of amla powder are phytochemicals gallic acid and ellagic acid. Gallic acid is a phenol molecule that has antiviral, antifungal, and antioxidant properties. It was also used to make ink in Europe and the Mediterranean regions for at least 2,000 years.  While it has not been studied for this purpose, perhaps gallic acid is the agent responsible for the anecdotal reports of gradual darkening of the hair when amla is used over time. Ellagic acid is a polyphenol found in many fruits, especially red ones such as raspberries. It is also documented to have antifungal, antiviral, and antioxidant properties.

These acids could also act as chelating agents to help remove some metals from the hair. Both gallic acid and ellagic acid can also combine with glucose, also present in amla powder, to form polymeric tannic acids.  These may also darken hair over time, as tea has also been used for its tannic acid to darken and dye fabric and hair. It seems doubtful that amla powder can prevent graying of hair or that it can perform any miracles, but it does seem as if it could provide some benefits to hair.

How to use amla powder

  1. Soak the amla powder in water to form a paste, which can then be applied to hair as a mask or used to scrub the scalp. The aroma from this fruit can be fairly unpleasant, so you can add a small amount of an essential oil or botanical extract to give it a more pleasant scent. 
  2. To prevent a mess, use a shower cap to cover your head while the mixture has some time to sit on your scalp and hair. 
  3. Once you have allowed the treatment to sit for a while, gently remove it by rinsing hair under warm, running water and carefully working it out of your hair.  
  4. Follow up with conditioner if your hair feels like it needs more slip.  
  5. Another way to use amla powder is to simply add some to a small amount of conditioner and apply it after it has had a chance to become slightly hydrated. Rinse normally.

Amla Oil

Oils labeled “amla oil” are actually perhaps more accurately called infusions of amla fruit in an oil base.

The carrier oils used are primarily sesame, coconut, almond, or mineral oil and sometimes contain other botanical extracts, such as Ayurvedic herbs, rosemary, and even henna.

It is likely that most of the effects of these products can be attributed to the oil and other actives in the product. Unlike the powdered fruit, these oils contain virtually no vitamin C, as it is not oil soluble. However, there may be some of the phytochemcials, gallic and ellagic acid, present in the oil mixture so it may provide some of the benefits, such as the antioxidant effects, as well as the antifungal and antiviral. Some darkening of the hair may also occur over time with repeat use, although this seems less likely than with the powder.

How to use it

If you wish to try amla in this form, look for one in a plant-based oil to derive the most benefit, and use it as you would coconut or almond oil. You can use it as a scalp treatment, a deep conditioning treatment, or simply add it to your leave-in conditioner, styling product, or directly to your ends.

It is always fun to try new things, or in this case, really old things. Although it is not likely to be a miracle cure for all that ails you and your hair, amla does sound as if it could provide some benefits for your hair and scalp.

Curlies will need to make sure they add plenty of moisturizers and emollients if they use the powder, as it does not have much to offer as far as conditioning on its own. If you already incorporate amla in your regimen and love it or tried it and hated it, we would love to hear about your experience!


Argan oil has been hailed as a cure-all for all your hair and skin care woes. The rave reviews are enough to convince anyone to put some argan oil in your shopping cart - that is, until you see the price. With a 1.7 ounce bottle costing up to $50 and so many other (cheaper) hair oils available on the market, any smart consumer would want to understand what exactly you're investing in.

NaturallyCurly's Curl Chemist, Tonya McKay, breaks down the science behind argan oil.

MORE: Argan Oil Hair Products

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Humectants can greatly help or hurt your hair's moisture levels. Understanding the science behind humectants will help you use them to your advantage.

 

 

Understanding Humectants

Humectants are materials used in products to moisturize dry or damaged hair.  They promote moisture retention by attracting water molecules from the local environment and binding them to specific sites along their structure.  

Adsorption vs Absorption

Absorption is the process whereby a substance passes into the bulk of a material and are dissolved uniformly throughout.   The solution cannot be easily separated into the original two substances.

Adsorption describes the process whereby atoms or molecules are attracted to and adhere to the surface of a material, usually via forces weak enough that they can be easily separated. Some humectants can adsorb several times their weight in water!

In humectants, this happens via hydrogen bonding - a very important phenomenon based upon polarity of specific atoms.

Polarity

Molecules are made of combinations of different atoms.  Sometimes the atoms have significant differences in their 'electronegativity', generating a charge separation where part of the molecule is more positive and the other is more negative.  When this happens, even though the overall charge on the substance is neutral, the molecule has distinct polarity. Imagine a magnet, with its positive end and negative end, and how they can link together end-to-end.

Molecules like water (H2O) have polarity due to the oxygen being much more electronegative than the hydrogen atoms.  The mildly negative oxygen atom is attracted to the mildly positive hydrogen atoms in other water molecules, and they move close to one another and form a bridge, called a hydrogen bond.  Each oxygen can form a hydrogen bond with two hydrogen atoms.  The triangular geometry  of water molecules allows them to stack together into a complex three-dimensional array.

Humectant molecules have polar hydroxyl groups (-OH) that also favor hydrogen bonding.  When applied to hair in a styling or conditioning product, they can attract water from the environment around them and bring it into close contact with the hair.

Humectants and Hair

When humectants bring water into contact with the hair, some can diffuse into the shaft of the hair.  This can add suppleness and softness to slightly dry hair.  It can make hair more bouncy and help it retain curl.  Hair can recoil more easily from mechanical stress and is less likely to break.

Humidity Concerns

In high humidity conditions, humectants may attract too much water to the hair from the wet environment.  This can cause the hair shaft to swell, the cuticle to become ruffled, and hair to lose its shape and become big and frizzy. Porous hair suffers from this problem more so than non-porous hair.  Some humectants may develop a sticky texture in these conditions as well.  This is not pleasant!

In extremely low humidity conditions, humectants may draw water out of the interior of the hair shaft and cause dryness and possible damage or breakage.  Use caution!

Humectants Can Help

  • Make hair feel softer

  • Make hair bouncier

  • Make hair more elastic and less brittle

  • Protect  hair from dry weather and wind

Humectants Can Harm

  • Can create frizzy, sticky hair in high humidity

  • Can dry out hair in low humidity

  • Can cause permanent damage to hair in either extreme condition

Common Humectants

Diols and Triols

Propylene glycol

1,2,6 hexanetriol

Butylene Glycol

Dipropylene glycol

Hexylene Glycol

Glycerin

Triethylene glycol

Erythritol

Capryl glycol

Phytantriol

Hexanediol or -triol beeswax

Humectants of biological origin

Panthenol

Sodium PCA

Hyaluronic acid

Inositol

Glycogen

Sugars and modified sugars

Sorbitol

Polyglyceryl sorbitol

Glucose

Fructose

Xylitol

Hydrolyzed proteins

Elastin, collagen, silk, keratin

Ethers

Isoceteth-x, Isolaureth-x, Laneth-x, Laureth-x, Steareth-x

PEG-x (polyethylene glycol)

Silicone copolyols

Structural formulae for some common humectants: Glycerin, propylene glycol, sorbitol, glucose, and sodium PCA (from left to right, top to bottom)  All images except Sodium PCA courtesy of Wikipedia. Sodium PCA image courtesy of chemblink.com.

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Uses of tea tree oil

A renewed interest in natural substances has increased the availability of tea tree oil as a home remedy, and has also inspired research into its composition and beneficial properties.  While it should never be taken internally due to potential toxicity, it is fantastic for topical treatment at home of

  • dandruff
  • hair growth
  • acne
  • ingrown hair
  • superficial wounds
  • bug bites
  • thrush
  • athlete's foot
  • fever blisters

Tea tree oil also acts as an anti-oxidant. It has been established in several preliminary studies that MRSA (methicillin resistant Staphylococcus aureus) is susceptible to topically-applied tea tree oil. Additionally, it is being studied for its potential use a treatment in some forms of cancer. While those are all rather lofty applications for tea tree oil, it also has benefits for personal care and cosmetic use.

Properties

 

  • antibacterial
  • antifungal
  • antiviral
  • anti-inflammatory
  • antiprotozoal
  • antioxidant

For your scalp

The antibacterial properties of tea tree oil enable it to be very effective in the treatment of acne, with fewer undesirable side effects than benzoyl peroxide.  This is excellent news for those who suffer from this problem on their body, face, or scalp.  It can also be used to treat areas of ingrown hairs or infected follicles caused by shaving.  As an antifungal agent, a shampoo or scalp massage oil that contains tea tree oil helps get rid of dandruff and cradle cap.  Tea tree oil is an effective solvent for sebum and other dirt or oily buildup on the scalp and hair, so it can be used to help provide a clear, clean surface that can absorb moisture and conditioning products more readily.  Additionally, scalp massage with tea tree oil can help stimulate blood flow and reduce inflammation in the follicular cells, which may help enhance hair growth. It is very important to dissolve tea tree oil into another oil medium prior to applying it to the skin and hair though, as it can be very irritating and drying when used in its undiluted form.

For your hair

Based upon its properties, tea tree oil is a viable solution for those with dandruff, itchy scalp, and problems with sebum buildup.  Preparing a solution that is no more than 5% by weight of tea tree oil and massaging it into the scalp and hair may provide excellent benefits.  It can be dissolved into a conditioner, shampoo, or a carrier oil such as olive oil, coconut oil, or jojoba oil.  While there is no definitive proof that it helps stimulate hair growth, it does seem likely to provide the optimal environment for scalp and follicular health, when applied occasionally in the proper concentration.  Remember that it is an effective solvent of oil, which means it can be stripping and drying if used too often or in too strong of a solution.  (Never use it straight!)  Using it as an occasional clarifying agent for hair that is predominantly conditioner washed or that may have buildup of styling product on it is may also provide some benefit and make it easier to rehydrate and condition your hair.  So use sparingly, and to good effect!

Compared to other oils

How does tea tree oil differ from other botanical oils often used for hair and skin care?  Botanical oils, such as coconut oil, shea butter, olive oil, jojoba oil, and almond oil are obtained via the pressing and mechanical extraction of the fats within the fruits from which they are procured.  These fats, called triglycerides, are large molecules comprised of glycerin with three medium chain fatty acids bonded to it.  The hydrophobic nature and physical structure of these oils enable them to behave as excellent lubricants and emollients for hair and skin.  Tea tree oil is an essential oil, which is obtained via steam distillation, fractional distillation, or solvent extraction of the leaves or stems of a plant.  The resultant product is a mixture of volatile organic compounds that have distinctive smells and useful properties, but which do not have the structure to act as lubricants or emollients for hair or skin.

Tea tree oil specifically is made up of dozens of constituents, the majority of which are terpenes, sesquiterpenes, and their corresponding alcohols. Terpenes and sesquiterpenes are a large class of naturally occurring compounds with strong medical relevance, as touched upon briefly in the previous paragraphs.  In addition to their medicinal properties, some (such as limonene and linalool) are used as fragrance additives in cleaning and cosmetic products. The major component in tea tree oil is the monoterpenic alcohol terpinen-4-ol, which comprises anywhere from 30-48% of the oil. Many of the complex benefits of tea tree oil have been attributed to this species.  Some of the components of tea tree oil are toxic or irritants though, which is why it should not be ingested and should be diluted when applied topically. Several cases have been reported where tea tree oil exhibited estrogenic and antiandrogenic properties, so for this reason, frequency of use, concentration of tea tree oil in the product,  and surface of area of coverage may be important factors to keep in mind.

Origin of Tea Tree Oil

Tea tree oil is a distinctively pungent essential oil obtained from the needle-like leaves of the Melaleuca alternifolia, a plant that grows in wet, marshy areas of New South Wales and Queensland in Australia.  It has long been prized by the indigenous Aboriginal people of Australia for its properties as an anti-infective and antifungal agent.  Commercial farming of tea trees (so-named by British explorer,Captain James Cook, circa 1770)  began once the medicinal properties of tea tree oil were studied, documented and published by Australian chemist, Dr. Arthur Penfold in the 1920’s). Subsequently, it became a common household remedy in Australia, and later was included as an indispensable tool in the medical and first aid kits for Australian soldiers during World War II. Demand for tea tree oil declined once antibiotics became widely available in the post-war era, and academic research focus also drifted toward more ‘modern’ topics.


Marketing statements for hair conditioners contain a variety of terms to describe the properties of the products in a manner that is enticing to consumers.  Included in these are familiar words such as: emollient, moisturize, seal, penetrate, repair, and condition.  Ingredient savvy consumers often seek to attribute specific properties, such as “emollient” or “moisturizing” to groups of ingredients in an effort to predictably define which products can meet the unique needs of their hair type. Due to some ambiguity in the usage of many of these terms, a number of questions come to mind when endeavoring to categorize materials in this fashion.

What criteria must be met for a product to be considered a hair conditioner? What are the exact definitions of the various marketing terms when applied to hair care products?  Are any of them interchangeable? What properties make an ingredient moisturizing, emollient, or conditioning? Is it possible for an ingredient to be both moisturizing and emollient? Are there more accurate and precise words that we could be using to describe these properties and ingredients?  Obtaining the answers to these questions can alleviate much of the confusion surrounding additives in hair conditioning products.

What is a hair conditioner?

A hair conditioner is a product which, when applied topically, can improve the overall quality of your hair's surface and bulk properties. Their benefits include increased slip between hair strands (and easier detangling), a smoother cuticle surface, decreased porosity, optimized hydration, decreased electrostatic charge, added body and bounce, and increased strength, suppleness, and elasticity.  Specialized products may also provide protection from thermal and UV damage, as well as improved color retention.   Some of these effects are purely superficial and temporary, requiring frequent reapplication to maintain the properties, while others impart long term benefits by the reduction of damage on a daily basis.

In order to achieve this high level of performance, a conditioner formulation must combine a complicated array of ingredients that both individually and synergistically contribute different properties to the whole package.  Generally, the most basic objectives a conditioner must meet are to provide hydration, lubrication, and occlusion to the hair.  Two common and often confusing terms used to describe the properties of various ingredients in the product are “moisturizer” and “emollient”.  These terms are used in variable ways in marketing statements and in the literature, and are a frequent source of confusion for users.

Moisturizers

The essential qualification for an ingredient to be a moisturizer is that it must improve or maintain hydration levels of hair or skin.  Proper levels of moisture (a delicate balance between too much and too little) help maintain the keratin structure and mechanical integrity of the hair.  Hair with optimal water levels has more body, bounce, and better curl retention.  Curly hair, with its greater porosity and complex protein structure is highly susceptible to water loss, and is thus in particular need of restoration of moisture on a regular basis.

True moisturizing agents are humectants, which are extremely hydrophilic molecules that use hydrogen bonding to attract and hold water molecules from the local environment, making it available to the hair. Some examples of these types of ingredients are glycerin, propylene glycol, panthenol, honey, agave, and aloe vera.  Additionally, a good moisturizing formula will include an occlusive agent, a hydrophobic ingredient which seals moisture into the hair by forming a barrier film on the surface of the hair.  There are some natural oils that have sufficient amounts of hydrophilic bits on their structures that they can act as both occlusive barriers and mild humectants, and some larger molecule sugars that have enough hydrophobic substance to also perform both roles.

Emollients

The term emollient is probably most appropriate for use in skin care applications, but it has been incorporated into the hair care vocabulary, which is often a source of confusion.   An emollient skin care ingredient is one that has good spreadability onto the skin, where it forms an evenly distributed film that softens and smoothes the surface without feeling greasy or tacky. So, if we extrapolate those properties to hair care, we can assert that an emollient for hair should easily form a smooth, even film on the surface of the hair, should soften the hair, and should not yield an unpleasant sticky or greasy texture.

More specifically, emollients for hair are usually hydrophobic oils that form films on the surface of the hair, where they often act as anti-humectants or sealers.  They are lubricants and provide increased slip (decreased drag) between adjacent hair strands, which makes detangling much easier.  They also reduce tangling in general by smoothing and flattening the cuticle surface, which can also add shine and gloss to the hair.  The best ones impart a soft, silky feel to tresses, while lesser ones may weigh it down or make it feel greasy.  Some can penetrate the interior structures of the hair and act as plasticizers, improving elasticity, toughness, and suppleness.

Common emollient ingredients include silicones (dimethicone, amodimethicone, cyclomethicone, etc.), fatty alcohols, fruit and vegetable-derived oils and butters, proteins and hydrolyzed proteins, mineral oil, petrolatum, and polyquaterniums (cationic polymers).  Many of these are entirely hydrophobic, but hydrolyzed proteins and fruit and vegetable oils are typically smaller molecules with fatty acid components that are hydrophilic.  This can enable these to act as both emollients and as mild humectants. Some of these can also penetrate through the cuticle layer into the cortex and significantly improve the mechanical properties of the hair (although for some people, this can weigh the hair down and disrupt curly pattern or swell the hair strand and raise the cuticle, creating frizz).  In extreme humidity, films comprised of these oils can become sticky and dull-looking due to inclusion of water molecules.

Most anti-frizz and anti-humectant serums are comprised of extremely hydrophobic, synthetic emollients such as silicones, emollient esters, and mineral oil or petrolatum.  These typically sit directly on the surface of the hair and act as occlusive agents, barriers which prevent moisture from escaping from the cortex or getting into it from a humid environment.  People who do not use shampoo or use only mild shampoos should be extremely cautious about these types of ingredients and products.

What You Need to Know

Good hair conditioners and hair treatments provide a variety of benefits, including optimizing the hydration and oil levels of your hair and protecting the surface.  Because the terms moisturizer and emollient are actually referring to fairly complex processes and multiple properties, it is not surprising that they are often used incorrectly or interchangeably, which can be confusing.  Marketing materials need to capture your attention quickly, but are not always entirely accurate in their oversimplified jargon.  For this reason, it is considerably more helpful for you as the consumer to determine what your individual hair needs are and to look for ingredients or combinations of ingredients that can meet those needs and to use specific, well-defined terminology to describe those ingredients.

Do you need a humectant to add moisture to your hair?  Do you need a slip agent to reduce tangling (oils, silicones, polyquats, simple quats)?  Do you need a fruit or vegetable oil to decrease porosity and to add softness and elasticity to your hair?  Do you need a water-repellent sealer to prevent frizz in your ultra-humid environment (silicones, mineral oil, serums, anti-humectants)?  Do you need a good conditioning agent to soften, detangle, or to give thermal and UV protection and increased color retention (amodimethicone, polyquats)? Knowing exactly what you want and need for your hair and understanding the terminology and properties of the various categories of ingredients can demystify and simplify the whole process.



A relatively recent addition to the vast portfolio of silicone ingredients available for use in hair care products appears to be gaining popularity amongst formulators, as it is present in a number of new products on the market.  This silicone has an INCI designation (international nomenclature for cosmetic ingredients) that is a mouthful, and it reveals little information regarding its nature to the typical consumer reading a label: propoxytetramethyl piperidinyl dimethicone.  As many people have become more particular about the ingredients they use on their hair, especially silicone derivatives, it is not surprising that this one gives some consumers pause as they wonder what it is and whether it is “okay to use.”  Since there are almost as many different definitions of “okay to use” as there are people who choose to offer their opinion on the matter, gaining an understanding of the chemical structure and properties of the ingredient can help aid you in making your own determination for your hair.

What is it?

Propoxytetramethyl piperidinyl dimethicone (henceforth PTMPD) is a unique, patented cationically-modified silicone described by its makers as a “hindered amino functional silicone fluid.”  It belongs to the same general category as other amine-functionalized silicones, such as amodimethicone and bis-aminopropyl dimethicone.  These silicones have been modified by adding pendant groups suspended from the main silicone chain that contain organo-amine groups (-R-NH2), which become positively charged in water due to electrostatic interactions.  The result is a cationic polymer (positively-charged) that possesses many exceptional beneficial properties for use in hair and skin care applications.

Amine-functionalized silicones are excellent conditioning and protective agents for hair, as they are drawn via electrostatic attraction to its negatively-charged keratin surface.  Once deposited, they spread easily into smooth films that form cross-linked laminate structures that encapsulate and protect both the cuticle and hair shaft.  They are highly valued for their ability to protect hair from thermal damage and to improve color retention.  They also impart a high degree of shine, making hair appear very glossy and healthy.  Like other silicones, they also ease detangling and give hair a soft, silky texture by reducing friction between adjacent strands of hair. Reduction of static electricity and fly-away hair is an additional benefit of these types of silicones.

What makes propoxytetramethyl piperidinyl dimethicone unique?

While propoxytetramethyl piperidinyl dimethicone shares similarities with amodimethicone, it is sometimes found to exceed the performance of amodimethicone in hair care applications.  The reason for this is its chemical structure.   PTMPD is synthesized by the addition of a sterically hindered amine group to the silicone polymer.  Steric hindrance is an organic chemistry term for limited access to a particular portion of a molecule due to the structure of the molecule being sufficiently bulky to physically crowd the site.  Hindered amines (piperidines) are valued for their ability to act as photostabilizers for polymer systems.  They act as radical scavengers, and thus perform well as anti-oxidants.

Is it Water Soluble?

This question always comes up in these discussions because some users prefer to not apply shampoos or soaps to their hair, and they want to use ingredients that can be easily rinsed off with water or with a mild conditioning rinse.  The simple answer to this question for this ingredient is “no”.  PTMPD is not water soluble.

Here is where confusion occurs, and it is worthwhile to attempt to provide some clarity.   The preparation of hair care products is a complex science involving the mixing of hydrophilic and hydrophobic substances together to create a product that consistently performs in the manner expected and retains its beneficial properties for a predictable period of time.  A fundamental scientific theory taught to us all at an early age is that oil and water do not mix. Fortunately, this inherent limitation can be overcome via the use of emulsifiers and stabilizers and mixing the ingredients in just the right order. It is unacceptable for the oils to separate from the aqueous phase, or for the preservatives to settle to the bottom, or for the opacifiers to crystallize and precipitate from the solution. Additionally, preparing the mixtures and emulsions should require the least amount of time and heat energy possible in order to maximize profit for the manufacturer.  This is not a trivial assignment, and the application of much scientific theory goes into the process.

Silicones bring added difficulty to the table for formulators and product manufacturers, due to their insolubility in both water and in most organic oils.  This requires them to be pre-emulsified by mixing them with multiple surfactants (usually a nonionic and cationic one) in water to form an aqueous emulsion or micro-emulsion.  The droplets of silicone form an aggregate with the nonionic and cationic surfactants and are suspended inside micelles (tiny spheres) that are dispersed in the aqueous phase of the solution.  The outer shell of these micelles is the hydrophilic portion of the surfactants, which renders these particles soluble in water.  This emulsion can then be added to an aqueous shampoo or conditioning product fairly easily.  To save time and resources at the final production site, oftentimes the raw materials manufacturer will simply provide the materials as a pre-made micro-emulsion.

So, it is important to remember that the PTMPD (and other amine-functionalized silicones) is not water soluble itself, but is grouped with other materials to make it be so for the sake of the product manufacturing process as well as for the  stability of the final product.  Once the product is applied to the hair, the positively-charged silicone and the positively-charged cationic surfactant both separately adhere to various negative sites on the surface of the hair, forming a protective, emollient film, and the nonionic surfactants are washed away.  The micelle cluster no longer exists, and the polymer is completely insoluble in water.

Once applied to the hair, propoxytetramethyl piperidinyl dimethicone is highly substantive due to the ionic bonds formed between itself and the negatively-charged surface of the cuticle. A powerful anionic (negatively-charged) surfactant is necessary to remove this type of polymer form the hair.  Even then, it may be highly resistant to removal. This property is considered to be favorable by most formulators, as it means that the benefits imparted by the ingredient will persist over multiple washings.  It does not build up on itself, and it does not attract organic oils to itself, so those will also not build up on top of it.

However, some users have expressed their belief that this persistent film caused their hair to become dehydrated, frizzy, or unpleasant in texture.  While this experience is not universal, this anecdotal evidence certainly cannot be dismissed or discounted.  One might also speculate whether the anti-oxidant properties diminish over time, or whether the optical properties of the film change and result in a duller appearance to the hair.


In closing, it is clear that amine-functionalized silicones provide many advantageous properties when used in hair care products. Among these are high gloss, lightweight conditioning, fewer tangles, and protection from thermal damage.  This particular polymer, PTMPD, provides even greater benefits in terms of color retention, sun protection, and intensive, targeted conditioning properties for damaged hair.  However, if one ascribes to shampoo-free methods of hair maintenance, this silicone might be too difficult to remove from your hair and could create unpleasant side effects over time.  If you have been displeased with the results of amodimethicone on your hair, this might be another silicone to avoid as well.  However, for most people, products containing PTMPD can be a really nice addition to the hair beautification and protection arsenal.


References

http://www.faqs.org/patents/app/20120178324 (HA info patent)

Urrutia, Adriana, Silicone: The Basis of a Perfect Formulation for Hair Care,

Dow Corning de Mexico S.A. de C.V.


What is Magnesium sulfate?

Magnesium sulfate is an ingredient often touted as a natural curl booster or curl activator for hair. It is typically used in leave-in conditioners and curl enhancers, both commercially available and homemade, and it is applied via a spray-on delivery method.

Many people have noted that their hair often responds remarkably well to the initial application, but further uses yield dry tresses that behave in an unruly fashion.  Several explanations have been put forth for this phenomenon, but there still remains some confusion as to why it happens.

By delving into the protein structure of hair and curls, and how magnesium sulfate interacts with these, we can gain clear understanding of the mechanism by which magnesium sulfate enhances curl pattern and retention, and also why the effects seem short-lived and eventually become unpleasant.

Hair Keratin Protein

Other types of crosslinking also occur between the polypeptide chains, and they also contribute to the structure of the hair. These two additional types of crosslinking are achieved via hydrogen bonding and formation of salt bonds and are sometimes referred to as secondary bonds. However, both of these types are physical crosslinks, rather than chemical ones (imagine it as two strands taped together or two magnets attracted to one another versus two strands sewn together or melted and re-formed into one object), and are susceptible to disruption via mechanical forces (touching or brushing the hair, wind) or the presence of water (swimming, washing, humidity, rain).Proteins are polymeric molecules (also called polypeptides) made up of many repeat units of various amino acids. The sequence, type, and order of the amino acids vary greatly depending upon the function of the specific protein. Hair is comprised of keratin protein, a polypeptide particularly differentiated from other proteins for its large proportion of cysteine, a sulfur-containing amino acid.  These polypeptide strands are crosslinked (bound together into a three-dimensional network) via formation of covalent bonds between adjacent cysteine residues. This linkage is a chemical crosslink referred to as the disulfide bond, and is the source of the strength and physical configuration of the hair. As the degree of disulfide crosslinking in a strand increases, so does the amount of curl in the hair.

Perms enhance curls by breaking the disulfide bonds via chemical means, curling the hair tightly to physically restructure it, and then re-forming the disulfide bonds at a higher percentage. Several researchers have found that hair is stronger and curl retention is increased when magnesium sulfate is incorporated into the rinsing and neutralizing agent used to re-form the disulfide bonds. They also noted that its use enhanced the curl pattern and imparted a greater stability to high humidity.

Magnesium sulfate

Magnesium sulfate, also known as Epsom salts, is an inorganic compound that exists as a hydrated material, magnesium sulfate septahydrate (MgSO4• 7H2O). This salt is extremely hydrophilic and thus easily dissolved into an aqueous solution that can be spritzed onto the hair. It attracts and binds water molecules from its surroundings to itself.  When MgSO4 is applied topically to hair it does not affect the covalent disulfide bonds, but it does impact the physical crosslinks formed by hydrogen bonds. By increasing the number of hydrogen bonds, the Epsom salt tightens the curl pattern of the hair.

The mechanism by which magnesium sulfate achieves this curl activation consists of two steps.

  • First, the magnesium neutralizes the excess negative charges on the surface of the keratin and brings it to its ideal pH (also known as its isoelectric point).
  • Secondly, a dehydration mechanism via a salt-protein interaction increases the quantity of hydrogen bonds (physical crosslinks), which makes the hair curlier.  This second part is what is critical to understand.

Hair keratin protein incorporates water into its structure. This moisture gives it softness and pliability and is why we strive to maintain properly hydrated hair. However, in a highly hydrated environment, the formation of hydrogen bonds between adjacent cysteine amino acids is minimal. But, in the presence of the highly hygroscopic salt, MgSO4, the keratin protein becomes dehydrated. This dehydrated environment is what permits the formation of additional hydrogen bonds and the curl activating properties of magnesium sulfate. Thus, the very quality that permits magnesium sulfate to boost curl formation is also the one that generates the poor results in subsequent uses.

Magnesium sulfate also forms fairly large crystals, and these structures can roughen the surface of hair, yielding an unpleasant texture and tactile experience for some. They may increase tangling as well, if adjacent hair strands get caught on them. For this reason, it is advisable to use a good lubricative leave-in conditioner along with a magnesium sulfate. (Dare I say it? A silicone might work nicely and not interfere with the curl forming effects of the MgSO4).

Magnesium Oil

Some products are beginning to advertise that they use magnesium oil, rather than magnesium sulfate.  These are typically a supersaturated aqueous solution of magnesium chloride (MgCl2). The chlorine molecule changes the properties of the salt, rendering it slightly less hydroscopic. For this reason, it may not boost curl as significantly, but also will not dehydrate and potentially damage the hair as much. It seems a reasonable type of product with which to experiment.

Take-home message:

Magnesium sulfate can indeed be a useful curl activator or curl booster and has a place in the arsenal of every curly girl (or guy).  However, the mechanism by which it achieves this effect leaves hair, especially fragile curly hair, very vulnerable to damage due to dehydration.  This effect can be minimized by using magnesium sulfate infrequently as an emergency agent, or using it in conjunction with products that deeply moisturize and protect the hair.  Definitely condition very well after every use!



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