Allegra-d side effects?

Insomnia, jitters: Allegra d contains 2 drugs. Fexofenadine usually has few side effects, but can be drying to the nasal membranes and mouth, and can have side effects, so check further if you have some. The d portion, on the other hand, is sudafed, and it commonly causes jitters, insomnia, fast heart rate, nausea and headache. It can raise the blood pressure and cause arrhythmias.