J.S.
I did with my first and my allergies were so bad that I was on allergy medicine every day for the last 10 years. I didn't have to take any allergy medicine during the whole pregnancy. It has to do with your lowered immune system - bad side is you can catch other viruses easier too. I never did so it was a win/win for me =)
Interestingly, with my second I was looking forward to the same benefit, but for some reason my allergies remained constant.