Cyproheptadine is an antihistamine primarily used to relieve allergy symptoms, such as runny nose, sneezing, and itching. It also has anticholinergic properties, which can lead to side effects like drowsiness and dry mouth. Additionally, cyproheptadine is sometimes used to stimulate appetite in individuals with conditions that cause weight loss. It works by blocking the action of histamine and serotonin in the body.