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.