Caffeine
Caffeine (CAS #58-08-2) is a heterocyclic organic compound with the chemical name 1H-Purine-2,6-Dione, 3,7-Dihydro-1,3,7-Trimethyl-. It is a small, water-loving molecule with good skin penetration abilities, widely known as a stimulant found in coffee, tea, and soft drinks. In cosmetics, it is listed under CosIng functions as a perfuming and skin conditioning agent, and is used across a wide range of skincare, eye care, body care, and hair care products.
Caffeine has antioxidant properties that reduce free radical formation and may help prevent UV-induced skin damage. It is associated with improving microcirculation, which is theorized to help with dark under-eye circles and puffiness, though double-blind research on a 3% caffeine gel found no significant difference from its gel base alone. It is also used for potential anti-cellulite effects via lipolysis stimulation and for hair growth, with one 2017 study finding a 0.2% caffeine liquid non-inferior to 5% Minoxidil in men with androgenetic alopecia.
Some claimed benefits (puffy eyes, anti-cellulite) are more hyped than backed by robust human clinical data; evidence for anti-cellulite effects is largely limited to animal studies or combinations with other actives.
