Triethanolamine (TEA) is an ingredient in cosmetics that serves as a tri-alcohol and amine — it’s a stabilizer that can be used to adjust the pH (Making Cosmetics). It’s a surfactant — which means it causes suds — and explains its uses in cosmetics and skin cleansing products (DOW).
It was shown in one study to help acidic drugs penetrate the skin (Biological and Pharmaceutical Bulletin).
The Cosmetic Ingredient Review panel and FDA both find TEA safe. The CIR declared it safe in formulas intended to be washed off and at a 5% concentration for formulas that will be left on the skin (National Toxicology Program).
There is some fear of toxicity because preliminary studies with rats show that it appears to be somewhat toxic to the liver of male rats, but not female rats (National Toxicology Program). Subsequently, it’s potentially toxic and more studies must be done to figure out the safety of TEA.
There’s also concern that because TEA is an amine that it could form nitrosamines when combined with nitrosating agents. An experiment where rats were dosed with TEA and nitrosating agents, researchers found there was no significant formation of nitrosamines (Regulatory Toxicology and Pharmacology). But other studies continue to hypothesize that TEA may play a hand in creating nitrosamines (Food and Cosmetics Toxicology).
The FDA and CIR have rated TEA as generally safe. It’s used as a surfactant and stabilizer in cosmetics. There are some studies that suggest it could be toxic, so it’s an ingredient to watch for further studies. It’s also been demonstrating not to form nitrosamines in one study, but many continue to be cautious about using it alongside nitrosating agents.