How exactly do you find out if you are allergic to semen? I keep reading all of these horror stories about women who find out they are allergic to their partner's semen and the really awful reactions and pain they experience. What I really want to know is - does the allergy only occur within the vagina? Sometimes, my boyfriend will go on my stomach for example (I'm on the pill, but we still like to play it a little safer if we can!) - if I were allergic to his semen, would it cause a rash on my stomach? Or would it only cause a vaginal reaction?