Charcot-Leyden crystals are endogenous hexagonal bipyramidal crystals present in human tissues and secretions. Presence of Charcot-Leyden crystals correlates with the increased numbers of peripheral blood or tissue eosinophils that occurs with parasitic and allergic processes. Galectin-10, also referred to as Charcot-Leyden crystal (CLC) protein, singularly makes up these crystals. Galectin-10, a member of the galectin family of beta-Galactoside binding proteins that bind to S-type animal lectins, is expressed solely in eosinophilic and basophilic leukocytes. Galectin-10 may possess carbohydrate or IgE-binding activities, and it plays a functional role in the biology of inflammation. Expression of galectin-10 is transcriptionally induced by butyric acid.