Could your shampoo cause cancer? Some say the active ingredient in many conventional shampoos has some severe health risks - that it’s a carcinogen, that it causes severe skin, eye, and lung irritation or blindness - but on closer inspection things may not be as dire as they seem. Sodium lauryl sulfate (SLS) is a common component in shampoos as a surfactant - it binds with the oil that your scalp produces, foaming up so you can wash it off with water. Though it has been deemed safe by the FDA for cosmetic use, there are concerns about the byproducts it creates contaminating the finished product, as well as its harshness and its effect on the environment.
SLS can be made naturally or synthetically.
Sodium lauryl sulfate, or SLS, is derived most often from coconut or palm kernel oil but sometimes it’s made from petroleum. Specifically, the chemical process that follows converts it to lauryl alcohol, then it’s mixed in a chemical reaction with sulfur trioxide to produce hydrogen lauryl sulfate, which is then neutralized with sodium carbonate. This can happen in a natural process or a synthetic one, which can end up as a biodegradable or non-biodegradable chemical, depending on that process. This has led to a lot of inconsistency when companies or chemists describe SLS as being natural or not - which as we have previously discussed is a vague term with no legal definition.
One chemical that can be created during the SLS compounding process is 1,4 Dioxane, which is listed as a carcinogen category 3 (the group between “possibly carcinogenic” and “probably not carcinogenic”), having been attributed to carcinogenic properties in animal testing. Just as the process that makes the SLS can vary widely, so does the presence of 1,4 Dioxane - it can be removed from the finished product, and some companies test for its presence.
An effective, but potentially irritating ingredient
As mentioned earlier, SLS is great for removing oil. It’s this property that makes it effective as a cleanser for cars, carpets, and engines - in much higher concentrations than it is used for personal care products. Since it makes a lathering foam when used, it’s found in many personal cleaning products - not necessarily because it does the cleaning job better, but because it has a psychological effect of “feeling cleaner” because of the foam. It also emulsifies liquids and makes toothpaste spread better. It’s an inexpensive, effective, and also visually appealing ingredient.
What makes SLS great as an engine cleaner can make it good for cleaning the body - but it is a harsh chemical. Most people can use it without a problem, but it has been linked to contact dermatitis in the past. The Cosmetic Ingredient Review determined that SLS is safe for products that are meant to be rinsed off quickly, and for products that have longer contact with the skin they shouldn’t use more than one percent concentration. At this concentration or less, SLS does have a drying effect, especially on dry and sensitive skin and more porous hair types.
While the more alarming attributes of SLS have been overplayed, the majority of the damage caused may not happen to your own skin or hair. Since most of the chemical ends up being rinsed off, it goes down the drain and can end up in the waterways. Though much of SLS is biodegradable, it’s surfactant property means it can profoundly impact marine life. Fish and other aquatic animals rely on a mucus layer to ward off bacteria, which means that the chemical is basically toxic. Studies have shown that the SLS that makes it into waterways from family households is degraded or diluted enough that the chemical is no longer toxic to marine life, but did not address the industrial sources of these chemicals - which would be of a different scale and concentration than consumer run off. As with so many industries, the choices we consumers if they don’t directly impact the environment, do create the demand to mass produce chemicals or other potentially hazardous materials.
Much of the coverage online could be fear mongering, but a lot of it is result of non-scientists reading reports on chemicals and misinterpreting. While sodium lauryl sulfate and similar ingredients most likely won’t cause adverse health effects, you may choose to steer clear for any number of reasons. Among those might be that you have sensitive skin, curly/kinky hair, or you just want to use the gentlest possible products on the hair and bodies of your family. You also may be concerned with the effects that these chemicals have once they go down the drain. If any of these reasons apply to you, there are plenty of alternatives.
By Ivory King
Written on 4/9/18