Amino acid complex

An amino acid complex is simply a blend of several amino acids working together in the same product. On the INCI list you will not find the phrase itself — you find the individual names, such as glycine, arginine, serine, alanine or proline, often sitting near sodium PCA and other components associated with the skin's natural moisturising factor.

In skincare, the blend usually acts as a humectant system: small, water-loving molecules that hold water in the outer layers and leave the surface feeling supple rather than tight. In haircare, amino acids are used for conditioning and slip, and their derivatives — names ending in glutamate or glycinate, for example — form the basis of some of the milder cleansing surfactants.

Read the term as a description of a category, not a promise. It tells you nothing about how much is present or how the finished formula performs, so the position of those ingredients in the list and the rest of the base matter more. Effects are cosmetic — hydration, feel and appearance — and patch testing new products is still worthwhile.