The Chemicals in Clean Hair
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When it comes to shampoo it seems that bubbles are what counts. Why? Because the bubbles show that the shampoo is cleaning our hair effectively.
Bubbles are created when the surface tension of the water is broken by a surfactant and air is trapped within the film of the soap. Unfortunately while bubbles may represent clean hair, more bubbles aren’t necessarily better for our hair or scalp. Some of the surfactants used in shampoos have the potential for scalp and skin irritation and hair damage.
We use many surfactants in our daily life, soaps and detergents, cleaning compounds, shampoos and a host of personal hygiene products. This article will look at two commonly used surfactants used in shampoo namely Sodium Lauryl Sulphate, and Decyl Glucoside. Both serve the same function in removing oil and dirt from skin and hair and being the base on which the hair cleaning products are built. That is where the similarity ends.
Sodium Lauryl Sulphate other wise known as SLS and other Sulphates are the most commonly used ingredients in shampoo. They are cheap, easy to formulate and provide plenty of bubbles and foam that we expect and like. Unfortunately this synthetic surfactant is the cause of many of the hair, scalp and skin problems that occur.
A study of the Material Safety Data Sheet of SLS provides us information about the hazard status of this product. It is moderately toxic and its contact hazard is also moderate however the issue is repeated exposure, such as regular use of a shampoo or body wash, which can lead to skin issues such as dermatitis. It has been used in medicine as a standard, or as a scale, to measure skin irritancy in comparing other chemicals. The irritation occurs even at concentrations of 0.5%.
Originally from plant origin, the starting material for this surfactant is Lauric acid, which is a coconut oil fatty acid. While the starting material may be natural (it also may be synthetic), during the conversion process to SLS, petrochemicals are added which means that the end product is nowhere near natural and may also retain contaminants such as 1,4, dioxane, a potential carcinogen. While the levels are minuscule, the potential for toxicity arises with repeated exposure.
From an environmental perspective, SLS is not biodegradable which may present wider issues for the ecology of our waterways.
The Hazards of SLS
In some soaps and shampoos the concentration of SLS may be as high as 30%. This is cause for alarm, considering the risk of dermatitis and skin irritation due to exposure at such high concentrations. In children this threat is enhanced due to the softer skin and it is advisable to look for SLS free products and products using mild surfactants.
In addition to the direct contact effects of SLS, many shampoos contain nitrate compounds. These compounds can react with SLS with the potential to form carcinogenic nitrates. Given the potential, however small for the creation of carcinogenic compounds, it is advisable to choose personal hygiene products that do not contain SLS.
Glycosides and poly glycosides, also called saponins are present in most plants. Some of these saponins are toxic however there are many saponins which are safe for topical or medicinal applications and even for human consumption as food. A wide variety of species, their geographical distribution, their applications and use by mankind are documented. Soap Bark (Quillaya), Soap Nut, Yucca Plant, Soap Wort, Horse Chestnut, Bracken and Soap Lily are a few examples of soap plants, from different parts of the world
Decyl Glucoside is a surfactant derived from two natural products, decyl alcohol and glucose. Decyl alcohol (Deca means ten) is produced from Capric acid. Capric acid itself is a fatty acid with a ten member carbon chain and is a constituent fatty acid of coconut and Palm oils (Coconut sources are preferable as the palms are sustainable). Capric acid is present to the extent of around 7% and 4% in coconut and palm oils respectively. Glucose, the other ingredient is produced from corn, maize and other starch based products.
It is important to clarify that a natural starting material does not necessarily equal a natural ingredient at the end of the manufacturing process. As pointed out with SLS, the addition of synthetic or petrochemical ingredients during the process of manufacture can completely change the starting material. While decyl glucoside is similarly changed from it starting material during manufacture, it does not carry the same risks of contamination as SLS so the end material is a very mild nonionic surfactant produced from corn, maize and other starch based products. Decyl glucoside is classified as ether in chemical terminology. It is produced by reacting decyl alcohol with glucose in the presence of an acid. The product is then purified and extraneous ingredients and reactants removed. Purified decyl glucoside is a liquid, which dissolves in water in any proportion.
Due to its mild nature on skin and its bio degradability, it is used in
shampoos, hair creams, lotions and other personal hygiene products including baby products. Generally decyl glucoside is much more expensive and labour intensive to produce and described as “tricky” to formulate with. Many products use decyl glucoside as a primary or secondary surfactant. It is a good emulsifier and has excellent foaming and lather properties. For this reason, the lack of potential for irritation and the absence of potential carcinogicity, decyl glucoside is a better choice in personal care items than SLS.
Some of the characteristics of Decyl Glucoside are
- Decyl Glucoside is an excellent emulsifier and produces good lather.
- Does not contain allergens,
- Is not a skin irritant
- No carcinogenic properties
- Chronic exposure symptoms have not been reported and no limits have been set on exposure to this product.
Decyl glucoside is by no means the only alternative to SLS however it is more and more commonly seen in shampoo and other personal care items and when it comes to choosing what to use on a daily basis, the more you know about the ingredients, the better. It also creates lots of lovely bubbles so lather away!
Author: Maree Watson, hairdresser and creator of the Eko Organica range of hair care. Edited by Ananda Mahony, naturopath and skin specialist.