How To Treat Large Hives During Pregnancy?

I'm 8 weeks pregnant and have a one year old breast fed baby too. I am 38 years old. I have suffered an allergic reaction day before and developed large hives all over my body. My gynae advised application of caladryl lotion, Last night i had a much stronger reaction covering my face and throat. Gynae said to take Avil, which I did not take as the symptoms seemed to subside. Now tonight again I can feel the rash begin to develop. Whats happening? I have been eating regular home food and avoiding soy which I initially thought was the cause. I've never had an allergic reaction before to soy or anything.Should I take Avil now?