An immune response against allergens contained in male ejaculate. Symptoms include vaginal burning, swelling and itching occurring approximately ten minutes after intercourse. While not rare, semen allergies are not overly common. They can develop right away with a new partner, or after a few years with the same partner. The allergy is often to one partner’s semen and not necessarily to all men’s semen. To differentiate from chronic vaginitis, a couple should use a condom to see if the symptoms stop. (They should use a polyurethane condom, as a latex allergy could mimic semen allergy symptoms.) Aside from a complete gynecologic exam, diagnosis should include intradermal testing, where a tiny bit of the semen is injected under the woman’s skin. Treatment under the supervision of an allergist or immunologist can include a graded challenge where dilute solutions of semen are placed in the vagina every 20 minutes until she can tolerate undiluted semen. The couple has to have intercourse at least once every 48 hours to maintain the desensitization. As is the case with food allergies, the semen allergy might go away as fast as it came.