Surfactants
Surfactants can be found in most shampoos. They're what make the shampoo lather, and the lather makes it easier to get the shampoo through the hair and onto the scalp. Surfactants are also the main "cleaning" agent in shampoos. They dissolve dirt and sebum ("oil") and leaves your hair and scalp squeaky clean. But, they also dry out the hair, and that's why we add conditioner. The sebum's purpose is to coat the hairs and lock moisture into the hair, but if we clean it off, we need artificial sebum - i.e. conditioner - to lock moisture into the hair. Since they are so drying, surfactants can be quite damaging to the hair. Even so, I'd say that most people don't feel it's socially acceptable to not clean your hair. So what do we do?There are several different types of surfactants, and some are harsher than others.
Anionic surfactants
These are typically the harshest, but also the most cleansing or clarifying.
Sulfates, sulfonates, phosphate esters
Examples:
- Sodium lauryl sulfate (commonly abbreviated SLS, the most common surfactant in shampoos)
- Sodium laureth sulfate (SLES)
- Ammonium lauryl sulfate
Carboxylates
Examples:
- Soaps
- Sodium stearate
- Sodium lauroyl sarcosinate
Zwitterionic or amphoteric surfactants
Examples:
- Cocamidopropyl hydroxysultaine
- Cocamidopropyl betaine
Nonionic surfactants
These are the most gentle surfactants, and are most commonly found alongside anionic or zwitterionic surfactants in a shampoo.
Examples:
- Cetyl alcohol
- Stearyl alcohol
- Decyl glucoside
- Lauryl glucoside
- Cocamide MEA
Cationic surfactants
Examples:
- Cetrimonium bromide
- Cetylpurdinium chloride
- Benzalkonium chloride
- Benzethonium chloride
Sulfate-free shampoos
You've probably seen companies advertising "sulfate-free" shampoos, or perhaps bloggers raving about it. Sodium lauryl sulfate (SLS), a type of sulfate, is the most common surfactant in shampoos. It's the most "effective" but also the harshest and most damaging. Products which are sulfate-free use milder surfactants and are then, arguably, less damaging. However, have a look at the ingredient list before you buy your new sulfate-free shampoo. Some sulfate-free shampoos have e.g. sodium lauroyl sarcosinate, which is an anionic surfactant (in the same group as SLS) and still pretty harsh. Sarcosinates aren't as harsh as SLS, of course. Different ingredients in the same group can have varying levels of harshness - e.g. ammonium lauryl sulfate (ALS) is anionic, and a sulfate, but still slightly milder than SLS.
If you want a good sulfate-free shampoo, I'd look for one with zwitterionic and nonionic surfactants. Nonionic surfactants are often so mild that they don't really "do the job" on their own, and a bit of zwitterionic surfactants can then add that little extra cleansing and lathering agency needed. One thing to think about when using sulfate-free shampoos, is that some (not all) lather a lot less than SLS-shampoos. This takes a little getting used to, and you need to really massage that shampoo onto your scalp. An idea could be to part your hair and shampoo different sections of your head systematically. Another idea is to dilute your shampoo with a bit of water in an applicator bottle, shake well, and then squirt the mixture onto your scalp before massaging.
More reading
Point of Interest!
"Surfactants!"
<http://swiftcraftymonkey.blogspot.se/p/surfactants.html>
Youbeauty
"The Science Behind Hair Products"
<http://www.youbeauty.com/beauty/the-science-behind-curly-hair-products/>
r/haircarescience
"big giant super basic ELI5 guide to cleansing your hair!!!" <https://www.reddit.com/r/HaircareScience/comments/1vw6sz/big_giant_super_basic_eli5_guide_to_cleansing >
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