Hello,,, yes tab. Allerga (fexofenidine), could rarely cause painfull menstruation or very rarely irregular periods. If so your periods will resume to normal once you stop it.
But before that there are few common things that can delay periods, that should be ruled out. Here are common condition that can delay periods - Overstress , Hormonal imbalance , Imbalanced diet , Weight loss ,
Thyroid diseases , Obesity , Depression , Ovulation deficiency , Polycystic ovarian diseases, or even pregnancy(if sexually active). If no symptoms are there regarding this then don't worry,, your periods will resume soon after stopping tablets.