A rare condition called Post-Orgasmic Illness Syndrome causes men to develop flu-like symptoms after they ejaculate. POIS was first reported in , but there's been barely any research conducted in the years since, and only around 50 cases reported in medical literature. To begin the process of better understanding exactly what the syndrome is and how it works, a team from the Department of Urology at Tulane University School of Medicine pored over the body of reputable research available, limited though it may be. Their review was published in the Journal of Sexual Medicine. POIS causes symptoms like those from allergies or the flu.
Men who get flu-like symptoms after sex might have rare illness
Post orgasmic illness syndrome (POIS)
Postorgasmic illness syndrome is a syndrome in which people have chronic physical and cognitive symptoms immediately following ejaculation in the absence of a local genital reaction. POIS symptoms, which are called a "POIS attack",  can include some combination of the following: cognitive dysfunction, aphasia , severe muscle pain throughout the body, severe fatigue , weakness, and flu-like or allergy-like symptoms,  such as sneezing, itchy eyes, and nasal irritation. The symptoms usually begin within 30 minutes of ejaculation ,  and can last for several days, sometimes up to a week. In some men, the onset of POIS is in puberty, while in others, the onset is later in life. The 7 clusters of symptoms of criterion 1: . POIS has been called by a number of other names, including "postejaculatory syndrome",  "postorgasm illness syndrome",  "post ejaculation sickness",  and "post orgasmic sick syndrome".
What It's Like to Have an Allergic Reaction Every Time You Orgasm
Men with post orgasmic illness syndrome POIS become ill rather immediately after ejaculation, whether spontaneously at night, during sexual intercourse or masturbation. Two subtypes are distinguished: primary and secondary POIS. It also occurs before or after a man has been sterilized. POIS is an invalidating most probably auto-immune disease leading to much distress in males and their partners.
Immediately after ejaculating, these men experience flu-like symptoms including a fever, runny nose, apathy, joint stiffness, and loss of short-term memory. Once thought to be a psychological illness, research from the Netherlands recently suggested that POIS may be caused by an allergy to semen. A Utretcht University team studied 33 Dutch men who reported POIS symptoms by giving them skin-prick tests using a diluted form of their own semen. Eighty-eight percent of the men tested positive for the allergy.