A latex allergy might mean that you need to seek out latex-free condoms, and a severe cat allergy might mean that you decide not to have sex at your kitty-loving date’s house. But what about a semen allergy? Yes, it’s rare, but some people are allergic to semen.
The official name for a semen allergy is human seminal plasma hypersensitivity, or HSP. It’s actually certain proteins in semen that cause this reaction, and some research suggests that food or medication may play a factor, too. In one case, a woman with a nut allergy had a reaction to her partner’s semen after he ate a Brazil nut. Semen allergies are quite rare, affecting up to 40,000 women in the United States. (People of any gender can have a semen allergy, but cis women are by far the most effected.) Researchers say semen allergies may be under-diagnosed because they are often mistaken for more common conditions, such as a yeast infection, an STI, vaginitis, or another allergy (for example, to lube).
Some people with semen allergies notice it the first time they have sex, while others develop it later in life. It’s possible for someone to be allergic to one partner’s semen but not another partner’s. It's even possible for someone to be allergic to their own semen, which is called post-orgasmic illness syndrome (POIS). Like other allergies, semen allergies may develop in adulthood. In fact, most people with semen allergies first notice symptoms in their 20s or early 30s. And just like other allergies, they may fade or disappear naturally over time.
Symptoms of a semen allergy are similar for people of all genders: you may experience redness, burning, pain, swelling, itching, or hives on any area that came into contact with semen. The vulva, vagina, shaft of the penis, and skin in the genital area are the most commonly affected, but symptoms can also appear in the mouth, the anus, the hands, and the chest. Some people also experience fatigue or flu-like symptoms. In severe cases, people can go into anaphylaxis, which requires immediate medical attention. Generally, semen allergy symptoms appear quickly, usually within half an hour of exposure.
“[If I get semen in my mouth], it makes my mouth feel super swollen and itchy. My throat feels itchy and then my stomach ends up feeling very unsettled. In my vagina, it was worse," one person with a semen allergy previously told Refinery29. "I realized I was allergic, because I went to the ER for something and they insisted I had an STI because my vagina was so swollen."
For most people with semen allergies, the solution is to simply use condoms during sex. However, some people will treat the allergy through desensitization (in which you’re slowly exposed to semen to build up tolerance, either with a diluted solution in a medical setting or by having sex without condoms once or twice a week). Taking an over-the-counter antihistamine before sex may also help reduce symptoms. If you have a semen allergy and want to conceive, your doctor may suggest in vitro fertilization (IVF) or intrauterine insemination (IUI).