There’s a mysterious phenomenon in which some men, immediately after having an orgasm, come down with a flu-like illness. Now Dutch scientists are saying these men may be allergic to their own semen. The condition is known as post-orgasmic illness sydrome, or POIS. Though it’s been on scientists’ radars for nearly 10 years, it’s not commonly known by patients or doctors. Many men who experience the post-ejaculate sickness don’t come forward and tell their doctor about it out of humiliation. Symptoms of POIS include fever, runny nose, extreme fatigue and burning eyes. They come on straight after climax and can last up to a week.