Medical researchers have found that some women are allergic to their male partner's seminal fluid, the thick liquid that carries sperm. Doctors know the disorder as “human seminal plasma hypersensitivity.” In rare cases, the allergic response can cause death. But there is good news. The malady is usually treated by allergists, although it takes some effort by concerned, caring male partners. To desensitize a woman's immune system against semen, doctors can either apply diluted samples of semen to a woman's vagina every 20 minutes, gradually increasing the concentration over the course of several hours, or the women can receive allergy shots containing small amounts of semen over the course of several weeks. Both techniques require sex two or three times a week to train their immune system. (Link)