The science of shampoo (part 1)

What is shampoo?

Shampoo is a mixture of a detergent (surfactant) and water designed to remove the greasy sebum that forms at the shaft along with dirt it attracts, without stripping our hair of all its natural oils. Shampoos contain the following ingredients:

•   foaming agents

•   foam boasting agents

•   modifiers

•   fragrance

•   preservatives

•   colorants

Personal care products and cosmetics are still among the least regulated products in most countries with many untested ingredients used which are only assumed to be safe.

If you have a look at a random store bought shampoo you will see many ingredients some of which you most likely will have no clue about. 

This is the ingredients list of a shampoo I got my hands on (I will leave out the name intentionally):

water, sodium laureth sulfate, coco betaine, cocamide MIPA, sodium chloride, sodium benzoate, sodium cocoate, sodium hydroxide, PPG-5-ceteth-20, PEG-55 propylene glycol oleate, PEG-60 hydrogenated castor oil, argania spinosa kernel oil, polyquaternium-10, salicylic acid, limone, camellia oleifera seed oil, linalool,benzyl alcohol, amodimethicone, propylene glycol, geraniol, citronellol, methyl cocoate, citric acid, laureth-5 carboxylic acid, hexyl cinnamal, fragrance.

So lets have a look at these substances:

Sodium laureth sulfate (SLS) is used as a detergent and surfactant and is found in almost every popular brand of shampoo. It is what actually leaves your hair clean. A detergent binds to both water and grease. When you apply shampoo to your hair and scalp the detergent adheres to the grease, it also attaches to the rinse water and leaves, taking the grease with it. So widely used yet SLS is considered a dangerous ingredient in personal care products and cosmetics. According to the AMerican College of Toxicity SLS stays in the body for up to 5 days. Some studies have shown that it causes malformations in children's eyes. Others have indicated that SLS can easily penetrate through the skin and enter and maintain residual levels in organs such as the the brain, heart, liver and lungs. When combined with other chemicals SLS can transfer into nitrosamines, a potent class of carcinogens. Therefore there are serious questions regarding the potential health threats of SLS. 

Coco betaine is used as a mild surfactant and foam booster is shampoos. Coco betaine is shorthand for the chemical cocamidopropyl betaine. It is made form coconut oil and a diamine called dimethylaminopropylamine, and it comes in the form of a pale yellow liquid. This ingrediant is generally regarded as a mild and safe ingredient, however it has been shown to cause allergic reactions in some individuals. 

Cocamide MIPA (Monoisopropanolamide) has serveral uses, including as a emulsifying agent, or an emulsion stabilizer, a surfactnat, a viscosity controlling agent, or a foam booster. It is another coconut-based ingredient which has been observed to cause allergies to the skin and lungs in some individuals. 

Sodium chloride commonly known as table salt is used as a thickener is shampoos containing sodium lauryl sulfate. It may cause eye irritation and a dry and itchy scalp. 

Sodium benzoate is a preservative. It is bacteriostatic and fungistatic under acidic conditions. The main concern with sodium benzoate is that when combined with ascorbic acid (vit C) or citric acid (which is usually present in shampoo!) it can convert to benzene, a known carcinogen. 

To be continued in second part of this post!

Image courtesy of  http://www.freedigitalphotos.net