Papain

Papain is a proteolytic enzyme used in exfoliating masks/cleansers (typically ~0.1–1%) that can disrupt the stratum corneum by digesting proteins, leading to stinging, erythema, and barrier compromise, especially on eczematous or compromised skin. It is also a known occupational allergen/respiratory sensitizer and has documented contact allergy/irritant reactions in susceptible individuals, so I treat it as a potent active that warrants cautious, gradual use and patch testing. Safety Notes: In consumer skincare, papain is commonly used at very low levels (~0.001–0.05%) in leave-on “enzyme” serums/creams and in rinse-off cleansers/masks where the enzyme is present mainly for mild exfoliation marketing and to avoid irritation and stability loss. Higher-strength OTC products (especially powdered enzyme cleansers, exfoliating masks/peels, and 2-step systems intended for brief contact) can reach about 0.5–2% papain (often declared as papain or as part of an enzyme blend), with these upper-end levels typically reserved for rinse-off or short-contact applications due to sensitization/irritation potential and activity control.