What it is
Chitosan is a linear polysaccharide produced by deacetylating chitin, the structural polymer found in the shells of crustaceans and in fungal cell walls. Its positive charge lets it bind to skin and hair and form a flexible film, which can improve substantivity, texture, and the sensory finish of leave-on products such as sunscreens. It also functions as a thickener and conditioning agent.
Safety & warnings
Chitosan is generally well tolerated topically and is widely used in cosmetic and biomedical applications. As a high-molecular-weight polymer it is not expected to penetrate skin significantly. Because most commercial chitosan is shellfish-derived, individuals with shellfish allergies may prefer to be cautious, although the relevant allergens are proteins that are largely removed during processing.
Origin & sourcing
Mostly natural-derived. It is made by alkaline deacetylation of chitin, which is typically sourced from crustacean shells such as shrimp and crab, though fungal and other non-animal sources also exist.
Questions everyone asks
Where does chitosan come from?
It is most commonly made from chitin in crustacean shells, such as shrimp and crab, though fungal sources are also available.
What does chitosan do in skincare?
It forms a light film on the skin, helps thicken the formula, and acts as a conditioning agent that can improve how the product clings and feels.