Are there any negative side effects if i take one 180mg allegra (fexofenadine) tablet daily for years? i have allergies all yr.

Probably not, but: New generation antihstamines are in general safe and effective. However, the best treatment for year round allergies is 1) avoidance of the allergic trigger; 2) antihistamines like allegra; 3) topical nasal steroid sprays (most effective); 4) allergy injections--will provide relief in majority of people and decrease need for medications.