I Had UTI In March 2018. I Was Under Medication

I had UTI in March 2018. I was under medication for 15 days. Immediately after stopping the course of medication for UTI, I stated getting skin allergy, in medical term, Urticaria. I am under medication for the last 4 months, taking Montek LC. Now I have been advised to take Montek LC twice a week. But the allergy is still persists if I stop taking this tablet. Doctor not able to say how long it persists. Please advice.