Protease

Protease is an enzymatic exfoliant used to break down keratin/protein debris at low percentages, but as an active enzyme it can disrupt the stratum corneum and provoke stinging, erythema, and barrier compromise in sensitive or eczematous skin. Enzymes (including proteases) are also well-recognized irritants and potential sensitizers in exposure contexts, and on compromised skin the irritation risk increases significantly, especially when layered with other exfoliants or acids. Given its active, barrier-altering mechanism and higher-risk profile for reactive populations, it warrants a significant-irritancy score. Safety Notes: In commercial skincare, proteases are most often used as enzymatic exfoliants in leave-on serums/creams and especially in rinse-off enzyme cleansers/masks/powders, where effective levels can be extremely low due to high catalytic activity (down to ~0.0001% active enzyme). Higher-strength consumer products—typically powdered enzyme exfoliants and wash-off masks—can reach about 0.5–2% protease/enzyme complex on an as-sold basis, though actual active enzyme content may be lower depending on dilution, carriers, and activity units. Leave-on formats usually sit at the low end because of irritation risk and stability constraints (pH, preservative compatibility), while rinse-off products tolerate the upper end of the observed market range.