I thought being allergic to peanuts would be a nightmare— but being allergic to sperm, while it's rare, can be extremely painful. Or, more specially, allergic to a certain protein in sperm. It's called human seminal plasma protein hypersensitivity (SPH) and although it's very rare it causes a lot of problems. Any area that's exposed to sperm (think genitals, throat, mouth, anus, etc) can break out in "redness, swelling, pain, itching, and a burning sensation", which sometimes stays where the seamen has touched but sometimes spreads through the whole body. While for many it subsides after 20-30 minutes, some women can have trouble breathing or even anaphylaxis. Scary stuff.
Leone Blackwell explains the experience on xojane: "I’m in pain, like I’m burnt... Every time we had sex, there was immediate pain and a burning sensation. The area would become red and swell up, then over the next week the skin cells would shed and fall off. I would be left in agony and the pain lingered for days."
Leone, like many other women, was originally misdiagnosed. Doctors are quick to jump to conclusions like thrush, especially if the symptoms are centered around the vagina. So what can you do if you suspect you have a semen allergy?
What to do if you suspect it
As I mentioned above, it's very rare, so if you're only having irritation in the vagina it could be something else. You can try testing if it's just a problem in your genitals by seeing if any itchiness or redness occurs when sperm is on your arm, leg, etc.
anyTalk to your doctor, explain what is going on and why you think it's an allergy. If the doctors suspects that it is SPH they can check with "intradermal testing, in which a small amount of the partner’s semen is injected under the skin". (I know this sounds weird, but you need to get on board with it now, I'll explain below.)
Now if you do have it, the most basic solution is to use condoms— that should solve the problem because you are not coming into contact with sperm. The only issue with this is, obviously, if you're trying to get pregnant. You can either try getting pregnant through in-vitro or, if you want to do it the old fashioned way, there are treatments available for the SPH itself. The good news is part of the cure (de-sensitization therapy) is that it requires your to have sex at least two to three times a week. Sounds great. The other part of the treatment involves either having gradually increasing amounts of sperm inserted into your vagina every twenty minutes or more shorts of the sperm under the skin (told you had to get on board). Luckily the therapies have proven very successful, so not too many people have to deal with the ongoing symptoms of SPH.