So what's wrong with SLS?

There is a fair amount of misinformation out there with respect to SLS (sodium lauryl sulfate) and its relatives as to why it should be avoided. The big one is that it apparently causes cancer. There is no peer-reviewed data that suggests that it is carcinogenic. At worse, these chemicals are strong skin irritants, and of course not natural. Upon closer examination though, we find that this is not the only story.

SLS belongs to a group of chemicals called surfactants. These lower the surface tension in liquids, allowing them to spread more easily, and in the case of soaps and shampoos, to make lots of foaming bubbles. There are a variety of surfactants used in bath and body care products, some of the more common ones being:

• SLS (sodium lauryl sulfate)
• SLES (sodium laureth sulfate)
• ALS (ammonium lauryl sulfate)
• SDS (sodium dodecyl sulfate)
• SMES (sodium myreth sulfate)
• BAC (benzalkonium chloride)
  
• Cocamide DEA and MEA
• Cocamidopropyl betaine
  

These are often made with coconut oil (or other natural vegetable oils) as the base and so you may see something like "derived from coconut" on the label. That should be a red flag and warrants further investigation. It is what they do to the coconut oil that is of concern. The oil is ethoxylated, that is, to put it simply, reacted with ethylene oxide and a strong base such as potassium hydroxide (KOH), to produce the surfactant. Ethylene oxide is produced from the hydrocarbon ethene (ethylene) - an obvious petrochemical. This is where the problem comes in. A by-product of ethoxylation is 1,4 dioxane, a potent carcinogen. It is the unintentional by-product that is the carcinogen, not the foaming agent itself, such as SLS. Nonetheless, if 1,4 dioxane is found in your personal care products, this is probably not a good thing.

That being said, it is probably a good idea to check your shampoo, lotion, toothpaste brand to be sure that if it does contain a surfactant, like the ones above, that independent testing has at least shown that it is not also contaminated with 1,4 dioxane. Additionally, because these surfactants are very strong skin irritants, its use, by people with sensitive skin and/or some form of contact dermatitis such as eczema, would seem to be contraindicated, and thus avoided.