SLS on the Label: The Molecule That Makes Foam and Sparks Debate
Arin Editorial · how this is made
The foam in your shampoo, the foam in your toothpaste. On the label you see a long name: Sodium Lauryl Sulfate, or SLS for short. It's a staple of cleansing products, but with a chemical-sounding name, it's natural to wonder: What is it, what does it do, and is it harmful?
What is SLS and what does it do?
SLS is a surfactant; it helps water and oil mix. It's found in shampoos, body washes, toothpastes and more. Its job is to clean and foam. It lowers the surface tension of water, lifting away dirt and oil. Foam also enhances that feeling. It's made from coconut or palm oil.
What does the irritation risk really say?
SLS is known to irritate skin and eyes. Records from the U.S. Environmental Protection Agency list various classifications, some of them severe damage. That describes the hazard, not what you'll necessarily experience in your product. Concentration and contact time matter. There is also a 'not classified' entry for skin sensitization; no strong allergen signal.
Where does the cancer claim come from?
The cancer claim actually targets SLES, not SLS. SLES is an ethoxylated derivative of SLS, and 1,4-dioxane can form during its production. IARC classifies that byproduct as a possible human carcinogen (Group 2B). But there is no direct evidence that SLES causes cancer. And SLS itself has no such classification.
Regulators and safety
In cosmetics, SLS is considered safe at low concentrations. SpecialChem ties irritation risk to high concentration and prolonged contact. Unilever says SLS has a good safety record. EPA lab screenings also found no effect on the estrogen receptor.
Its use in cosmetics at low concentrations is considered safe; irritation warnings exist, but it is not linked to cancer.
If you experience itching, redness, or mouth sores, you can switch to a gentler cleanser. If you have no reaction, there's no concrete reason to avoid it. Toothpaste can also irritate, especially if you have canker sores; a sulfate-free toothpaste is an option.
Sources
- EPA ToxCast / ToxValDB