You realized after fifth grade that cooties don’t actually exist. But it turns out that being “allergic to boys” is possible…in a way. If you’ve ever dealt with itching or burning after sex, you could be experiencing an allergic reaction to your partner’s semen. (Related: Asking for a Friend: What’s Causing My Itchy Vagina?)
But before you go and declare yourself allergic to sex, keep in mind that there could be other more common excuses for your symptoms, like an infection. Semen allergies (also referred to as sperm allergies) are pretty uncommon, but not unheard of. One 2011 study estimated that some 40,000 women in the U.S. could be affected. If you have a reaction every time you have sex without a condom, and never when you have sex with a condom, that’s a sign that a semen allergy might be to blame, says Alyssa Dweck, M.S, M.D., FACOG, coauthor of The Complete A to Z for Your V: A Women’s Guide to Everything You Ever Wanted to Know About Your Vagina. (Err, you should probably take this time to read up on eight scary condom mistakes you could be making.) Dr. Dweck says that most of the women she sees in her office with a semen allergy assume—without ever being tested—that their irritation was caused by a yeast infection. (Now’s the time to read up on the five biggest yeast infection myths.)
When it comes to irritation from semen, you could have a mild sensitivity or a full-blown allergy, says Dr. Dweck. What’s more, women who suffer from semen allergies experience varying degrees of severity in their symptoms. The most serious but rare cases can cause wheezing or difficulty breathing. More commonly, women will have a local reaction with a rash, hives, redness, or swelling that lasts about an hour after having sex. Taking an antihistamine before sex can help guard against a reaction for women who experience more severe symptoms, but using a condom is the best way to prevent these uncomfortable side effects, says Dr. Dweck.
Other disturbing facts: Semen allergies can develop over time, and just like you can be allergic to walnuts but not peanuts, you can be allergic to one man’s semen and not another’s. “It’s partner-related,” says Dr. Dweck. “So you can have sex with one person and have no trouble, but then have sex with another man whose semen causes some sort of a reaction.” Well, guess that’s one way to weed out incompatible partners.
For more answers to your uncomfortable sex questions, check out: Is It Possible for a Guy’s Penis Size to Be Too Big? and The Real Reason You Can’t Orgasm During Sex.