Sever Urticaria on the 10th day of a 15 day course of Nitrofurant...

Sever Urticaria on the 10th day of a 15 day course of Nitrofurantoin for chronic UTI. The urticaria has already lasted 2 weeks and has not subsided yet. Taking Antihistamines. This is the third such instance of urticaria after taking Nitrofurantoin in the last 7 years. In the previous 2 instances urticaria started weeks after finishing the antibiotics course hence could not associate it the drug. Doc feels it could be drug induced liver cholesterol which is causing the itching. I am a 34 yr old female