Antihistamines
Antihistamines such as Allegra (fexofenadine), Claritin (loratadine), Zyrtec (Cetirizine), and Benadryl (diphenhydramine) block the effect of the chemical histamine, which the body produces in its attack against allergens. They can provide much-needed relief of allergy and cold symptoms, including sneezing, itching, watery eyes, and a runny nose. Unfortunately, these drugs also do a number on your eyes, reducing the watery tear film that keeps them moist.