Antihistamine pills and liquids work by blocking histamine to relieve watery, itchy eyes. They include cetirizine (Zyrtec), diphenhydramine (Benadryl), fexofenadine (Allegra), or loratadine (Alavert, Claritin), among others. Some may cause drowsiness. Antihistamine eye drops work well for itchy, watery eyes.