Pronounced “kahy-tuh-san” is a clearing agent to control spoilage yeast. Chitosan is a fibrous substance made from shrimp shells and the shells from other crustaceans. It is used as a fining agent in wine making, and works slightly differently from Kieselsol. Both Kiesesol and Chitosan should be used to clarify wine and used in the correct order: first adding Kieselsol and then Chitosan. If you accidently add these in the reverse order, wait about 3 days, rack your wine, and then add them again in the correct order. Chitosan is also used in some cheese making processes. Although it is derived from shellfish, there is no danger of allergic reactions to the product, as there are no allergens left after Chitosan is processed.