A number of side effects occurred in less than 2 percent of people who were taking Allegra - Fexofenadine (or the percentage of these side effects could not be determined). As a result, it is difficult to tell whether these side effects were caused by Allegra or some other factor.
Some possible rare Allegra side effects include but are not limited to:
Sleep problems, including insomnia
Allergic reaction
Painful menstrual periods
Unexplained rash
Nervousness
Swelling of the lips, mouth, or throat
Difficulty breathing.
Final Thoughts on Side Effects Seen With Allegra
You may experience some or none of the side effects listed in this article. Unfortunately, there is no way for your healthcare provider to know beforehand if you will have side effects from a medicine that you have never tried. Therefore, make sure to let your healthcare provider know if you develop any side effects with Allegra. Also, let your healthcare provider know if you develop something that “just does not seem right.” While it may not be a side effect, your healthcare provider will be able to diagnose and treat the problem.