Displaying 6 results of Clemastine Impurities Clemastine is an antihistamine medication used to treat allergies and itching. Like all drugs, clemastine may contain impurities that can affect its potency and safety. These impurities may arise during the manufacturing process or storage of the medication. It is important to monitor the levels of impurities in clemastine to ensure its quality and efficacy. Any impurities above the acceptable limit can pose health risks to patients.