Levocetirizine Dihydrochloride is the active enantiomer of cetirizine, a second-generation antihistamine used for the relief of symptoms associated with allergic rhinitis (hay fever) and chronic urticaria (hives). It works by blocking the effects of histamine, a substance in the body that causes allergic symptoms such as sneezing, runny nose, itchy eyes, and skin rash. Levocetirizine has a high affinity for histamine receptors and is known for its potent antihistamine effect with minimal sedative properties, making it suitable for daily use.