can benadryl lower seizure threshold?
However, pseudoephedrine and dextromethorphan can also lower the seizure threshold and are common ingredients in many cold medications. Guaifenesin does not seem to be as much of a problem. Some people are also sensitive to antihistamines, so we suggest that you avoid diphenhydramine (Benadryl) and cetirizine (Zyrtec).