Why is Allegra Used?

Fexofenadine is a prescription antihistamine. It is a second-generation antihistamine and selectively inhibits binding of histamine to type 1 histamine receptors, thereby reducing the incidence of sedation experienced with older antihistamines. Antihistamines compete with histamine for histamine receptor sites. By occupying the histamine receptor sites, antihistamines prevent histamine from its actions. 

Fexofenadine is indicated for adults and children 6 years or older to temporarily relieve symptoms caused by hay fever and allergies (runny nose, sneezing, itchy/watery eyes, scratchy nose or throat). It is available in a variety of forms, including tablets and capsules, and combined with a decongestant (Allegra-D).