Q. why do your products contain sodium lauryl sulfate or SLS? i’ve heard that is a harmful ingredient.
A. i’m so glad you asked that question. there’s nothing i like better than an answer that lets me spout science.
for some reason, SLS is an ingredient that has been buried in misinformation. lots of people have heard they should be avoiding it, but almost all the rumors around SLS are false. (remember that I said “almost” all. I’ll address this later.)
a lot of unsubstantiated claims have been made about sodium lauryl sulfate’s alleged links with cancer. these rumors are the easiest to dispel, since there is zero scientific evidence that links the two. this information is backed by the American Cancer Society.
another rumor seems to imply that other, similar, ingredients offer a healthier alternative to SLS. this is a confusing issue, and to understand it i’m afraid we’re going to have a teeny chemistry lesson.
first, let’s investigate what exactly SLS is, and how it’s made.
SLS is a surfactant, which is the cleaning agent in a formula. most stains–especially oily stains–won’t rinse away on their own in water, which is where surfactants come in. surfactants are the workhorses that pull grease and dirt away from whatever surface you’re cleaning. you’ve heard the phrase “oil and water don’t mix.” and that’s true, unless we’re talking surfactants.
surfactants are unique because their molecules contain both hydrophilic and hydrophobic ends. the hydrophilic end gravitates towards water (hydro = water; philic = loving) and the hydrophobic end gravitates away from water and towards oils and other stains (hydro = water; phobic = afraid). so the hydrophobic end pulls the oils from the surface, and the hydrophilic end transports the entire molecule, with the stain, into the water solution.
so now we know what a surfactant is, but what’s the deal with SLS?
sodium lauryl sulfate is part of a group of similar surfactants that I’ll call S_Ss. apart from SLS the most common ones used in cleaning are sodium coco sulfate (SCS) and sodium laureth sulfate (SLES). (you may also see sodium caprylic sulfate, sodium oleic sulfate or sodium stearyl sulfate.)
there are a few small but important differences between S_S surfactants. but let’s start with what’s the same.
all of the S_S surfactants start from what are called fatty acids. these fatty acids can come from a bunch of different sources, including petroleum or coconut oil. at the point of manufacture, fatty acids derived from petroleum are identical to fatty acids derived from coconut. we use the ones that come from coconut, because that’s a renewable source. the surfactants are named after the fatty acid they’re made from. so when you see sodium lauryl sulfate you know it was produced from lauric acid, and when you see sodium stearyl sulfate you know it was produced from stearyl acid.
however… in the case of sodium coco sulfate the ‘coco’ refers to a blend of fatty acids. in fact it comes from lauric, myristic, palmitic and stearic acids.
some companies that use sodium coco sulfate seem to want you to believe that it’s different from sodium lauryl sulfate. but the fact is that SCS actually contains SLS, along with sodium caprylic sulfate, sodium capric sulfate, sodium oleic sulfate, sodium stearyl sulfate… and potentially a number of other S_Ss too. as we said, it’s a blend.
so what about sodium laureth sulfate? well, the process used to make SLES is the same one used to make SLS, except for one important difference. the –eth on the end refers to a process called ethoxylation. in this case, ethoxylation is used to make the ingredient gentler. however ethoxylation can also produce a contaminant called 1, 4 dioxane, a dirty ingredient. 1, 4 dioxane has been linked to cancer and is on the State of California’s prop 65 list of known carcinogens. it is possible to buy sodium laureth sulfate that has been stripped of the 1, 4 dioxane contaminate, but it’s always a good idea to check with the manufacturer to make sure that is in their specifications.
i mentioned a few paragraphs back (before you dozed off during the chemistry lesson) that almost all the rumors surrounding SLS are false. however, one concern that some people have about SLS is that it can cause skin irritation–and this can be true in certain cases. the cause can be traced back to SLS’s properties as a surfactant. its effectiveness relies on the oil-loving end of the molecule pulling off oil stains, but it can also remove other oils, including beneficial oils on the skin. because of their oil removing properties, surfactants can be drying. that’s one reason many of our products that will touch your skin, like hand wash and body wash, include moisturizers like aloe vera.
hopefully that answered your question. sorry if it was a little lengthy, but now you know that “SLS” also means “saskia loves science”.
saskia is our resident greenskeeping manager, though we like to call her “captain planet.” got a green question for saskia? email it to email@example.com. questions will be chosen at random and answers will be posted on our blog.