Apparently there are women who are actually allergic to semen, that stuff that contains men’s sperm which comes out when a man ejaculates (in case you missed sexual health 101 in high school:) 

Semen allergy is basically just like any other allergy, in that it irritates the place that it touches, the woman’s vagina, and it can be so severe in some women with this precarious allergy that it can actually induce anaphylactic shock. 

Women who are THIS allergic to men’s semen are actually urged to carry around an epipen, which is a self injected shot of epinephrine, more notoriously carried around by those with severe bee sting allergies in case they are stung. 

This means that women with severe allergies to semen can actually die if they are exposed to semen and are not treated within adequate time to reverse the allergic reaction to it.  It is a fairly rare condition, but actually many women have a very light case of semen sensitivity. 

The process by which medical professionals can help women with semen allergy is to do sort of a desensitization treatment where women are exposed to varying amounts of semen to desensitize their bodies to the presence of the foreign substance in their body and therefore overcome the body’s natural allergic reaction to the stuff. 

Doctors also prescribe frequent sex to women with semen allergies, so that they may further their contact with the substance and help to desensitize themselves further on an ongoing basis, and hopefully cure themselves of this unfortunate allergy once and for all.  Semen volume enhancers for men with partners with this allergy would probably not be recommended, fellas!