Caffeine

Caffeine is primarily used as a vasoconstrictive/anti-puffiness antioxidant, typically at ~0.1–3% in eye products and serums, and it is generally well-tolerated on intact skin. Clinical experience and patch-test data suggest low inherent irritancy, but stinging or dryness can occur in eczema-prone or barrier-impaired patients—especially in the periocular area or when paired with other actives—so it is best classified as gentle rather than very gentle. Safety Notes: In commercial skincare, caffeine is commonly used at very low levels (~0.01–0.1%) as a secondary/label-support ingredient in general moisturizers, cleansers, and body products, while eye-area de-puffing serums/creams and “energizing” leave-on treatments more typically sit around ~0.3–1%. High-strength consumer-available leave-on eye serums and slimming/firming body gels have been marketed up to about 5% caffeine, which is near the practical upper end due to solubility, crystallization risk, and sensory irritation constraints; rinse-off formats rarely justify higher levels because contact time is short.