The betaine, or trimethylglycine, is a natural compound extracted from sugar beets. It belongs to the humectant family and is one of the molecules that the skin itself uses to regulate its water balance.
It works as an osmolyte: it draws in and retains water in the superficial layers, helping cells maintain their water content even when the environment is dry. It also plays an important formulation role, because it makes cleansers more tolerable by reducing the harshness of surfactants — one of the tangible ways in which a cleanse becomes truly gentle.
It is found in cleansers and formulas for dehydrated skin, where it works alongside other humectants. It acts within the product, without any leave-on time or frequency limits.
It is a dual-purpose ingredient: it hydrates while also improving the performance of the formula it is part of. In a cleanser, this means being able to clean effectively without leaving the skin feeling tight, which is the most difficult compromise to resolve in cosmetics.