Papain is a protein enzyme with papaln proteinase, chymopapain and lysozyme. Enzymes accelerate reactions within body cells. In the human body, the pancreas usually produces enzymes that break down foods into nutrients that the body can use for energy and other functions.

Papain is an enzyme produced by the tropical fruit, papaya. Papain is proteolytic, which means that it digests proteins. Enzyme deficiencies are rare, but individuals who have cystic fibrosis or diseases of the pancreas may not produce enough natural enzymes to digest foods properly. Frequently, papain is included in prescription combinations of digestive enzymes to replace what individuals with these conditions cannot produce naturally. Because it improves digestion in general, papain has been used orally to treat less serious digestion disorders such as bloating and chronic indigestion. Since parasitic organisms are largely proteins, papain has sometimes been taken internally to eliminate intestinal worms, but this use is rare today.

Topically, papain has been used for skin conditions such as psoriasis. Its ability to break down proteins is used to remove dead tissue from burns, to help skin injuries heal, to remove warts, and to treat ringworm. Cold sores caused by Herpes zoster virus have been treated successfully with both oral and topical papain-containing products. In one small study of individuals with Herpes zoster, an oral papain product was as effective as a prescription antiviral medication in resolving pain, but not redness. Further study is needed to prove or disprove this effect, however.

As recorded in the Dictionary on Traditional Chinese Medicine, the papaya contains papain, which can help cure cancers, and kill the lymphatic leukemia cells, probacteria, parasite and bacillus tuberculars, helping diminish inflammation, normalize the functioning of the gallbladder, alleviating pain and promote digestion. Meanwhile, it has stronger curative effect on gynaopathy, glaucoma, osteoproliferation, healing of wound, blood grouping and insect bites. The papaya powder, on the other hand, can help promote the blood circulation in one's breasts and make them healthier. Putting the papain into some mixed forages can greatly increase the availability and inversion of protein, decreasing the cost for forages and exploiting sources of protein. For example, the papain can used as additives in the forages for such animals as pigs, oxen, sheep, chicks, ducks, geese, fish, shrimps, eels and cows. Papain can be made into depilatory for tanning the leathers, making the products smooth and shiny. Papain can be used for processing wool, boiling off cocoons and refining silks. In this way, the products won't shrink and will be quite soft. Since the pain can dissolve sericin but is unable to affect silk fiber protein, it can be used for the refinement of the mixture of bombycine and vinegar fiber, and for the refinement of the Chinese crine. Papain can help dispel taches ad pimples, clean you face, promoting the blood circulation, making you skin healthier and tender. Due to its characteristic of superoxide dismutase ( SOD ) and properties of MT, the papain can keep one's skin from sunburn.