Betaine (seen on its own in an ingredient list; not to be confused with cocamidopropyl betaine) is a naturally-occurring amino acid (trimethylglycine) obtained as a by-product of sugar beet molasses. Betaine is a moisturizing humectant, not a surfactant. It can enhance the texture and height of foam, so it may be added to cleansing formulas for that reason, in addition to its moisturizing and protective properties.