What is it?
A cleansing and foam-boosting ingredient made from coconut oil. Its molecule carries both a positive and a negative charge, which puts it in the same family as the betaines; sultaines are sometimes called sulfobetaines. It is used mostly in shampoos, body washes and bath products, where it cleanses, builds foam, helps thicken the formula and conditions hair and skin.
Key information
- The CIR Expert Panel concluded in 2018 that cocamidopropyl hydroxysultaine is safe as used in cosmetics.
- It is not ethoxylated and, unlike cocamide DEA, is not made with diethanolamine.
- The Panel recommends that it not be used in products where nitrosamines can form, and at high concentrations it severely irritated eyes in animal tests.
More information
Suppliers told the Cosmetic Ingredient Review (CIR) that cocamidopropyl hydroxysultaine is made by reacting coconut oil with dimethylaminopropylamine (DMAPA) and then with a chlorinated sulfonate (3-chloro-2-hydroxy-1-propanesulfonate). In 2018 it was reported in 280 products, mostly shampoos, bath soaps and body washes, at up to 11.5 percent in rinse-off cleansers and 2.5 percent in leave-on face and neck products.
The CIR Expert Panel reviewed it with 12 related sultaines and concluded in 2018 that they are safe as used. It did not irritate rabbit skin, and it caused no allergic reactions in human repeated-insult patch tests at up to 4 percent, although one test at 2.5 percent produced slight to moderate irritation. One person has been reported with an allergic reaction to shampoos containing it. At concentrations up to 41.5 percent it was a severe eye irritant in rabbits. Tests for genetic damage were negative.
How does it compare with cleansers the Foundation rates Red Light? It is not a sulfate, and its name has none of the markers the FDA links to 1,4-dioxane. Unlike cocamide DEA, it is not made with diethanolamine. The Panel did raise two manufacturing points. Leftover DMAPA can cause skin allergies, so it urged manufacturers to keep it to a minimum; suppliers reported typical levels below 10 parts per million. And because the ingredient contains an amide group and may carry amine impurities, the Panel recommended that it not be used in products where nitrosamines can form, the same caution it attaches to cocamide DEA.
Sources: Cosmetic Ingredient Review: Safety assessment of alkyl sultaines as used in cosmetics (2018); Cosmetic Ingredient Review: Quick reference table, safe-with-qualifications findings (2020); FDA: 1,4-Dioxane in cosmetics, a manufacturing byproduct
