When you get redness, swelling, and itchiness down there, it’s easy to assume it’s a yeast infection, or perhaps an STD. But experts say it may actually be a sign of an allergy to semen causing your symptoms. While rare, a semen allergy can happen, and they’re not always easy to detect. Here’s what you need to know.

According to the International Society for Sexual Medicine, a semen allergy is a rare allergic reaction to proteins found in a man’s semen that mostly impacts women.

Common symptoms include redness, swelling, pain, itching, and a burning sensation in the vagina that usually starts about 10 to 30 minutes after you have contact with semen. Symptoms aren’t just restricted to your vagina, though: They can happen on your skin or in your mouth as well.

Naturally, a sperm allergy can make it difficult to get pregnant. However, the ISSM says women with this allergy can still get pregnant through artificial insemination or IVF, and the allergy shouldn’t impact the pregnancy.