Chitin is a cellulose-like biopolymer found mainly in the exoskeleton of marine animals such as shrimp, crabs, or lobsters. Chitin can also be found in mushrooms and yeasts. Chitosan is a chemically processed form of chitin. "Squid pens," waste shell by-products of squid processing, are a renewable and inexpensive source of chitosan.
Chitosan has been used in water purification plants to absorb greases, oils, metals, and toxic substances. Chitosan has been used in the cosmetic and fabric industry.
There is some evidence of the effect of chitosan on lowering cholesterol and body weight, but the effect is unlikely to be of medical importance. Chitosan dressings are sometimes used in emergency rooms to control bleeding. Chitosan has been used in various drug delivery systems. Antimicrobial and other effects are being evaluated for use in dentistry.
Chitosan has been administered at wide-ranging doses in clinical studies. In studies evaluating weight loss, 2.4 g/day is commonly used.