Another unfortunate side-effect of Gulf War Syndrome
Possibly, says early-days-yet vague hunch scientific study.
[…] we did some work on the burning semen syndrome in men who, after coming back from the Gulf War, were complaining of burning and pain after ejaculation or after contact with their own semen.
Thankfully, semen allergy mostly affects women. Via Gareth’s comments in Chris’s livejournal.