Cyproheptadine HCL is an antihistamine used in pharmaceutical formulations to treat allergic conditions such as hay fever, rhinitis, and urticaria (hives). It works by blocking histamine receptors, which helps alleviate symptoms like itching, swelling, and sneezing. Additionally, Cyproheptadine is known for its appetite-stimulating effects, making it useful in treating anorexia and malnutrition.