Cyproheptadine HCL is an antihistamine medication used to reduce symptoms of allergic reactions, such as sneezing, itching, and runny nose. It is also used to treat other conditions, such as hay fever, hives, and itchy skin. Cyproheptadine HCL is available in tablet and syrup form. It is also available as a powder, which can be mixed with water or other liquids to make a solution.