CurlChemist looks at the different kinds of silicones and what exactly they do.

Q: Some of the ingredients in my products have names that look a lot like names for silicones. What are they? Are they silicones? Should I be concerned about how they may affect my hair if I am avoiding strong surfactants (sulfates) in my hair care routine?

A: It gets confusing, doesn’t it? There are so many different ingredients approved for use in personal care products, and sometimes their INCI names (International Nomenclature of Cosmetic Ingredients) start to sound very similar. Chemical nomenclature (organic or otherwise) is a pretty in-depth topic, and there are several different naming conventions of which INCI is only one. Rather than tackling that beast, let’s simply take a look at some of the ingredients frequently confused with silicones and try to get some clarity around this issue (at least with a few ingredients!).

First of all, what is a silicone?

A silicone is a polymer or oligomer with an inorganic (non carbon-based) backbone, typically with organic pendant groups. The structures of silicone polymers or cyclic oligomers (such as cyclopentasiloxane, cyclomethicone) always include silicone atoms and oxygen atoms as part of the backbone of the molecule. These molecules are used in a wide variety of products, typically for their superior conditioning effects and their ability to impart gloss and shine.

Many curly-haired consumers who have delicate, dry hair avoid frequent use of shampoos containing strong surfactants. People who adhere to a low sulfate or sulfate free shampoo routine often avoid products containing silicones because they are almost always water insoluble (with a few exceptions) and can cause problematic buildup on the surface of the hair if not removed via a shampoo. For this reason, they read labels of all the products they use and occasionally experience confusion when an ingredient has a name similar to the silicone family of ingredients.

Figure 1. Generic structure of a silicone molecule – note the presence of silicon and oxygen atoms.

Following are some examples of ingredients whose names sometimes raise red flags for those consumers concerned about the presence of silicones in their products:

5-Bromo-5-Nitro-1,3-Dioxane

5-bromo-5-nitro-1,3-dioxane (trade name Bronidox) is a six-membered cyclic ether, a member of a group of molecules known as –oxanes. This name is easily confused with the very similar notation used for many silicones: polydimthylsiloxane. Bronidox is an antimicrobial and preservative that is especially effective against yeast and fungi. It is slightly less soluble in water than alcohols, but it is present in hair product formulations in such low percentages that there is no concern whatsoever about buildup on the hair, regardless of hair-care routine (no shampoo, low shampoo, etc.)

Figure 2. Structure of Bronidox

Isothiazolinones: (methylisothiazolinone and methylchloroisothiazolinone)

Methylisothiazolinone (MIT) and methylchloroisothiazolinone are preservatives that are usually sold and used as a mixture (trade name: Kathon CG). They are part of the ketone family, a group of organic compounds, and the –one at the end of their name can be confused with the –one found in the names of some silicones. These chemicals are highly effective against yeasts, molds, and both gram negative and gram positive bacteria. However, they are considered to be very strong allergens and irritants of skin and membrane tissue. Some studies have also led to questions regarding potential cytotoxicity and neurotoxicity (although the FDA and CTFA do currently state that the products we use containing these chemicals are safe). Safety considerations aside, these preservatives are water soluble. Even if they were not, they would not be present in appreciable enough amounts to be a source of build up.

Figure 3. Structure of methylisothiazolinone

Isododecane, Isohexadecane

These ingredients are branched alkanes (-ane), which are molecules comprised only of carbon and hydrogen. Isodocane and isohexadecane are small, branched molecules, and are chemically very pure due to their synthetic origins. These hydrocarbon olefins are not petroleum distillation byproducts as many other raw materials often are, but are synthesized via highly advanced processes from very pure starting material.

They are used in cosmetics due to their low toxicity, low skin irritation, no color and no odor. Isododecane can be used as s solvent for higher molecular weight water insoluble components such as silicones. Isohexadecane is valued for its non-greasy or tacky feel and its ability to impart a silky, smooth texture to skin and hair. It has excellent spreadability for both skin and hair also. Neither of these molecules is a silicone, but they are both insoluble in water. Due to their fairly simple and compact hydrocarbon structure, I would not expect problems with buildup if one were using a conditioner cleansing routine.

So what does all this tell me?

Hopefully we have shed some light on a few ingredients that get confused with silicones from time to time and helped you understand the differences between them and silicones and (more importantly) whether they are okay for you to use with your particular hair routine. The bigger take-away message is that many of the ingredients listed on cosmetic packages can be strikingly similar and certainly confusing! When in doubt, look it up, ask a friend, or ask the chemist! I am always happy to answer your questions.