Papain is the enzyme on which almost the entire enzymatic peeling category is based, yet it is one of the least explained ingredients in cosmetics. Those who search for it online mostly find products to buy, and rarely anyone explaining how it works - and, above all, what truly distinguishes it from an exfoliating acid.
Article written by Elisa Avalle, founder of LeLang Skin Care and dermocosmetics specialist. Cover image generated with the support of artificial intelligence.
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What is papain?
Papain is a proteolytic enzyme, meaning a protein capable of breaking down other proteins. It is extracted from the latex of the unripe fruit of Carica papaya by making an incision in the skin and collecting the liquid that emerges, which is then dried and purified.
It belongs to the class of cysteine proteases: at the enzyme's active site, a cysteine residue directly participates in breaking the peptide bond. This is the same mechanism by which papaya has been used for centuries to tenderize meat — the same reaction, applied to a different substrate.
In INCI, it appears as Papain.
How papain works on the skin
Dead cells in the stratum corneum do not fall away on their own: they remain anchored by protein junctions called desmosomes. Exfoliation always involves weakening those bonds in one way or another.
Papain does this by directly breaking down the proteins that make up those junctions. Mechanical friction, as with a scrub, is not needed, nor is it necessary to lower the skin's pH as with acids.
It has one quality that no other method possesses: the enzyme works as long as it finds substrate, and when the available proteins are used up, it stops on its own. Enzymatic exfoliation is self-limiting by design, and cannot go beyond what is necessary even if left on for longer.
Compared with other enzymes, papain also works across a wider pH range, making it easier to stabilize within a formula.
Enzymatic peeling and acid peeling: the real differences
There is a widespread misconception here, and it is worth clarifying.
| Enzymes | Acids (AHAs and BHAs) | |
|---|---|---|
| How they work | Break down desmosome proteins | Weaken the bonds by lowering the pH |
| Formula pH | Close to physiological | Acid, necessarily |
| Depth | Superficial | Variable depending on the acid and concentration |
| Self-limiting | Yes, the enzyme becomes depleted | No, it depends on time and concentration |
| Photosensitization | Not a characteristic | Yes, sun protection is essential |
However, beware of a widespread oversimplification: it is often said that « an enzymatic peel does not contain acids ». That is not automatic. Many products on the market combine enzymes and acids in the same product, in which case the precautions for acids apply. The only way to know is to read the INCI.
Papain and bromelain: two enzymes, not one
They almost always appear together and are treated as synonyms, but they are not.
Papain comes from papaya, while bromelain comes from pineapple stems. Both are proteases, but they recognize different protein sequences: each cuts at points the other does not recognize.
That is why a well-formulated product contains them together: they cover a broader range of bonds and distribute the work instead of concentrating it on a single type of target.
What is papain used for in skincare
Papain is the first choice for those who want to exfoliate but cannot tolerate scrubs and acids: uneven texture, dull complexion, skin that seems to stop absorbing anything.
Use it once or twice a week, in the evening, respecting the indicated contact time. Skin appears brighter and more receptive from the very first application: it is one of the few treatments whose results do not require weeks of waiting.
In LeLang formulas, papain works alongside mandelic acid, the AHA with the larger molecule and more gradual action. This combination produces an exfoliating effect by distributing the work across two different mechanisms, rather than relying on the strength of a single active ingredient.
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How to store a papain product
It is the information missing almost everywhere, and it concerns the very nature of the ingredient.
Enzymes are proteins, and like all proteins they denature: heat, light, and time progressively reduce their activity. An enzymatic peel forgotten in the bathroom during summer, or kept beyond the recommended period after opening, loses effectiveness without any visible change in the product.
The practical rule is simple: keep it away from heat sources, close it tightly after use, and follow the period indicated by the PAO, the open-jar symbol.
Who needs to be careful
Papain is extracted from papaya latex, which has a practical consequence: people allergic to latex may experience cross-reactivity with certain fruits, including papaya. This is known as latex-fruit syndrome.
Anyone with a known allergy to latex or papaya should therefore test the product on a small area before regular use and speak with their doctor in the event of significant previous reactions.
Frequently asked questions about papain
Is an enzymatic peel suitable for sensitive skin?
It is the most suitable exfoliation method when scrubs and acids are not tolerated, because it requires neither friction nor an acidic pH. It is still an exfoliating treatment: on very reactive skin, it is best to start with one application per week and short contact times.
Does leaving the enzymatic peel on for longer make it work better?
No, and this is one of the advantages of this technology. The enzyme is depleted once it has finished the available substrate: leaving it on longer does not increase exfoliation, it only increases contact time with the other ingredients in the formula.
How often should a papain peel be used?
Once or twice a week is the usual frequency. As with any exfoliant, the rule is not to layer two treatments in the same routine: if you use the peel, skip the acid or retinol that evening.
Does papain cause photosensitivity like acids?
Photosensitization is a typical characteristic of alpha hydroxy acids, not enzymes. That said, any freshly exfoliated skin is more exposed: wearing sunscreen in the following days remains the sensible choice, and becomes essential if the formula combines enzymes and acids.
Can I use papaya pulp on my face instead of a peel?
Papain is concentrated in the latex of the unripe fruit, not in the ripe flesh that is eaten, and with a homemade preparation there is no way to know how much is present or control its pH. The result is unpredictable and, on already reactive skin, not necessarily gentle.
Are papain and bromelain too harsh when used together?
No: they recognize different protein sequences, so together they distribute the work instead of concentrating it on the same target. This combination is specifically designed to make exfoliation more even and less concentrated.
In our ingredient glossary you will find the papain information sheet, including its INCI and the LeLang products that contain it.
