Papain

What it does

Papain is a cysteine protease enzyme extracted from Carica papaya. In cosmetics it acts as an enzymatic exfoliant: instead of dissolving intercellular adhesion with acids (as AHAs and BHAs do) or mechanical scrubbing, papain breaks down the proteins holding dead cells together so they shed more easily. One caveat is often stated backwards: keratin is the protein papain digests LEAST readily, at 6% hydrolysis against 35% for collagen in skin-substrate testing. It is not a keratin-selective enzyme. In vitro studies confirm its proteolytic activity on skin protein substrates. The exfoliation is gentler than high-concentration chemical acids, making it an option for skin too reactive for AHAs. Enzyme activity depends heavily on formulation — papain requires an appropriate pH range and is sensitive to heat and poor packaging. Latex-allergic individuals should exercise caution as cross-reactivity with papain has been reported, though it is uncommon.

The evidence, graded

Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.

Also known as

papaya enzyme, carica papaya enzyme, papaya extract enzyme

Pairs worth knowing