My Dr gave me a prescription for Generic Cialis, I got hives

I have taken name brand cialis in the past with no issues. Not recently however, its been at least a few years.

My urologist prescribed tadafil, I got it filled at Costco, they gave some 20mg tabs. I took about 1/2 a pill. a day later I started getting hives. I thought it was poison ivy or some other type of reaction, but now I am not so sure. Its been a week since I took it, I keep finding new hives popping up on my legs and arms.

I don't have any other issues except the hives that are itchy AF.