Elastin

Topical elastin is typically used as a moisturizing/film-forming protein (often hydrolyzed) at low concentrations and is not considered an active that alters skin physiology like acids or retinoids. Clinical experience and patch-testing data generally show low irritancy for protein humectants/film formers, but as an animal- or marine-derived protein it carries a small risk of irritation or sensitization in highly reactive or eczema-prone patients, so I do not score it as inert. Safety Notes: In commercial skincare, elastin (typically hydrolyzed elastin or soluble elastin from marine/animal sources) is most often used at very low levels (~0.01–0.3%) in leave-on creams/serums and eye products as a marketing/conditioning protein due to cost, odor/color, and stability constraints. Higher-strength consumer-available “elasticity/firming” concentrates and ampoules can reach ~1–5% active elastin/protein solids (sometimes presented as higher % of an elastin solution rather than true protein content), while rinse-off formats generally sit at the lower end because deposition is limited.