Breathing difficulties some women have after sexual intercourse could be an allergic reaction, doctors in the United States said.

In extreme cases, doctors said, some women experience difficulty breathing and hives after intercourse, ABCNew.com said. If women have an allergy, symptoms usually are milder -- a reddening and swelling of the vaginal area that disappear within a few hours.

Proteins in the semen are the culprits, ABCNews.com said, and using a condom is the simplest treatment. Also an antihistamine, a vagina-specific allergy medication or injections will help, especially if it is a mild reaction. But sufferers must visit their gynecologists to ensure no other infection is present.

If a woman is trying to conceive, her gynecologist can inseminate the sperm "washed" of semen directly into her uterus, ABCNews.com said.

Of course, there could be other reasons for a post-intercourse reaction. If condoms are used, the woman could be experiencing a latex allergy, ABCNews.com said. Other possible causes include lubricants and spermicides.

Copyright 2006 by United Press International