Antihistamine APIs are a class of compounds widely used to treat allergies and allergic reactions. These compounds work by blocking the effects of histamine, which triggers allergy symptoms such as itching, sneezing, runny nose, and watery eyes. Protheragen offers a full range of antihistamine APIs to support your research, including first-generation antihistamines such as diphenhydramine and chlorpheniramine and second-generation antihistamines including cetirizine, chlorpheniramine tadine and fexofenat.