Used as an antihistamine in pharmaceutical formulations to relieve allergic symptoms such as sneezing, runny nose, itching, and watery eyes. It is commonly found in over-the-counter cold and allergy medications, often combined with other active ingredients like decongestants or analgesics. Due to its sedative effect, it may also be included in nighttime sleep aids. Additionally, it is used in ophthalmic preparations to treat eye allergies and inflammation. Its anti-allergic properties make it effective in managing skin reactions such as hives and itching when applied topically or administered systemically.