I wouldn't expect it's the Allegra. They're both antihistamines -- just different ones -- still, chemically, the same kind of drug. Why don't you stop by your pharmacy and ask your pharmacist to look up Allegra and tell you if there's a mention of the sleep problem with it. Really, that's the best place to go for your answer. The other thing you could do is switch back to Zyrtec or try Claritin and see if the problem goes away.
Fexofenadine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
* headache
* dizziness
* diarrhea
* vomiting
* pain in the arms, legs, or back
* pain
* pain during menstrual period
* cough
Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:
* hives
* rash
* itching
* difficulty breathing or swallowing
* swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
* hoarseness
* difficulty swallowing or breathing
Fexofenadine may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.