Hello,
Topamax can cause itching and erythematous rash in some individuals.Although the main
side effects of topamax are slower reflexes, trouble thinking or concentrating, tiredness, poor coordination, and dizziness,yet it has shown itchy skin in some individuals.
I feel that if you are showing any allergic reaction to topamax,pls stop taking it and consult your doctor for a change in prescription.You can take over the counter antihistaminic like benadryl or Claritin for itching.