I agree with Halls and Chiggins1066, I think you are just prong to bladder infections. I too have the same problem and my Urologist has given me Macrobid to take immediately after intercourse. It is also a good idea to empty your bladder before and after intercourse. I also drink one glass of cranberry juice everynight before I go to bed. I do not believe this is an allergy, I just think our anotomy is not "routed" quite right!
Hope this helps.

Yes, Macrobid is the best!!!! I know many of women who take it right after they have sex and it helps prevent UTI's etc.... I get UTI's occasionaly and when I do i always take Macrobid.

Halls