You may want to exercise caution when using soaps on your hair
Natural, organic, healthy, naturally-derived, plant-based, renewable, green, pure: Close your eyes and throw a dart inside a beauty supply store and you will be hard-pressed to not hit a target with at least one of these buzz words on its label. The current marketing trend is so prevalent that it is a rare personal care product indeed that doesn't make some sort of claim to be healthier, more natural, better for you or the environment. We are inundated with a plethora of information via all forms of media regarding the way ingredients in products may affect our health and well-being.
All of this hype can lead to people feeling very uneasy and even outright fearful, and product development and sales people are more than happy to capitalize on those concerns. The result can be high-quality new products becoming available to the consumer, but it can also be labels loaded with misleading information, false claims, and even real duds in terms of performance. The buyer must be savvy. In a series of articles, I will be addressing a few topics related to this green marketing campaign and do some educating and myth-busting . This month I will discuss soaps in shampoos and skin cleansers.
Shampoos and skin cleansers are a huge sector of the personal care market. In recent years, there has been a real (perhaps not entirely undeserved) backlash against products that contain sodium lauryl sulfate and other similar synthetic surfactants, so there has been a huge research and development push in the industry to provide more mild and "natural" products. Those of us with delicate, curly hair are always on the prowl for products that will cleanse well, but leave our locks healthy and silky. So in many ways this is a fantastic trend for us. A wider variety of products are now available that contain milder surfactants than the sulfates and that also contain plant oils and emollients that help restore moisture to the hair.
However, there is one ingredient that is a great example of how natural and old-fashioned is not always an improvement. I am referring to soap-based shampoo bars and shampoos that contain ingredients called "plant oil soaps" or "organic saponified plant oil." In past articles, we discussed the chemical nature of soap molecules, soap bars, and how they work and the potential problems they present for curly hair (Shampoo and soap bars, Porosity and Curly Hair). Please have a look at those if you would like a more in-depth discussion about soaps.
To briefly review, soap molecules are surfactants made from reacting natural fats (triglycerides from animal or plant sources) with a very strong base (usually sodium hydroxide (lye) or potassium hydroxide (potash)) to form ionized, alkaline fatty acids. This reaction process is called saponification, and while it has been used by humans for many centuries to make soaps, it really isn't any more natural than many other forms of synthesis that take place in a laboratory. Saponification is a rather environmentally friendly process, though, so soaps can be set apart from the detergent crowd for that reason.
Soap molecules are anionic surfactants (just like sodium lauryl sulfate, but with a different head group), materials that have both hydrophilic (water-loving) and hydrophobic (water-hating) moieties, and as such are reasonably effective at removing grease and oil from hair, skin, and clothing fibers. However, they come with a set of complications that do not occur with most other synthetic surfactants. A brief summary of the drawbacks of these soap molecules is that they have a much higher pH than is ideal for hair, and permanent damage to the cuticle and lipid layer of hair strands can occur when these products are used. They also react with minerals found in hard water to form an unpleasant film of soap scum and mineral scale on the hair, which can lead to a rough texture, tangling, breakage, and a general dry sensation. Hard water also significant affects the cleansing efficacy of soaps. For these reasons and more, synthetic surfactants are used in commercial products more often than soaps.
How and Why are Soaps in my shampoo or facial cleanser?
Typically we think of soaps as being solids, but it is possible to dissolve solid soap into an aqueous solution to form a liquid shampoo or skin cleanser formulation. Another way to do it would be to take the neat soap solution that is the product of the saponification reaction and add excess water and other ingredients directly to that mixture. The primary difference between liquid and solid soap is that liquid soap is made via reaction with potassium hydroxide rather than with sodium hydroxide. The reason for this is due to the larger atomic size of potassium which enables the molecules to remain further away from one another in solution, thus preventing flocculation and precipitation. A pure liquid soap is clear, but most products have additives such as fragrance, viscosity modifiers, pearlizers, emollients, emulsifiers, and preservatives.
The ingredients list of a shampoo or skin cleanser will indicate the presence of soap molecules using terms such as "olive oil soap", "coconut oil soap", "corn oil soap", "soap of jojoba oil", or "organic saponified avocado oil". These are not specifically approved INCI terms for these ingredients, but they do make it pretty easy to spot them in a product. Liquid cleansers and shampoos that contain soap molecules will have most of the same drawbacks of a soap bar, but may be more gentle simply due to being less concentrated.
Soaps are so appealing on a natural and health-conscious level, as they are made with many fewer chemicals using natural plant oils in a very environmentally friendly process. Unfortunately, they do have many drawbacks in terms of performance, and there are other naturally-derived cleansers that are less harsh for curly hair. However, if the soap is listed lower down the ingredients list (meaning it truly is a minor component of the product), the pH of the product may be lower (more acidic) and thus the product may not be less harsh than one with a high concentration of soap. If the rest of the product looks appealing to you, it might be worth trying it to see how it works for you. I always feel the best data is obtained by the end user when they experiment with a product on their own hair, so don't be afraid to try something new if it looks like the soap is not the major component.