What is it?
A cleansing and foaming agent made by joining lauric acid, a fatty acid, with sarcosine, an amino acid found naturally in muscle and other body tissues. It lathers well and is used mainly in body washes, bath products and shampoos. Despite the similar name, it is not sodium lauryl sulfate: it is not a sulfate at all, but a fatty acid joined to an amino acid.
Key information
- The CIR Expert Panel concluded in 2016 that sodium lauroyl sarcosinate is safe as used when formulated to be non-irritating.
- It is not a sulfate and is not ethoxylated, so it does not carry the 1,4-dioxane concern linked to sodium laureth sulfate.
- Because its starting material, sarcosine, can form a nitrosamine, the Panel cautions against using it in products where N-nitroso compounds can form.
More information
Sodium lauroyl sarcosinate is made by reacting sodium sarcosinate with a fatty acid chloride and neutralizing the product. The Cosmetic Ingredient Review (CIR) reported 485 uses in 2016, mostly in bath soaps and body washes (230) and shampoos (113), at up to 15 percent in rinse-off products.
Its name is easily confused with sodium lauryl sulfate (SLS), but the chemistry and test results differ. The CIR describes SLS as an irritant in patch tests at 2 percent and above and limits it to 1 percent in products that stay on the skin. Sodium lauroyl sarcosinate was not irritating or sensitizing in human studies at 2 to 5 percent, and in 2016 the Panel dropped its earlier 5 percent limit for leave-on products. It can still irritate: a 10 percent solution caused clear redness on rabbit skin, and two people have been reported with allergic reactions to cleansers containing it. That is why the Panel asks that products be formulated to be non-irritating.
It is not ethoxylated, so it is not among the ingredients the FDA links to 1,4-dioxane. The open question is nitrosamines. Sarcosine can react with nitrosating agents to form N-nitrososarcosine, which causes liver cancer in animals. Tests of the raw material found no nitrosamines, at a detection limit of 15 parts per billion, and manufacturers do not use nitrites or nitrates. Even so, the Panel cautions against using it in products where N-nitroso compounds can form, the same caution it attaches to cocamide DEA.
Reality check: sodium lauroyl sarcosinate is not SLS in disguise. On labels, check the spelling: “lauroyl sarcosinate” is this ingredient, while “lauryl sulfate” is SLS.
Sources: Cosmetic Ingredient Review: Amended safety assessment of fatty acyl sarcosines and sarcosinate salts (2016); Cosmetic Ingredient Review: Sodium lauryl sulfate and sodium laureth sulfate safety summary; Cosmetic Ingredient Review: Quick reference table, safe-with-qualifications findings (2020); FDA: 1,4-Dioxane in cosmetics, a manufacturing byproduct
