A mysterious flu-like sickness that affects some men after they've had an orgasm is exceedingly rare, but scientists warn its prevalence may be greater than we know due to under-diagnosing of the illness.
The condition – called Post-Orgasmic Illness Syndrome (POIS) – was only first reported in 2002, but since then some 50 cases have been documented, in which men experience a range of flu-like and allergic symptoms after ejaculation.
These symptoms, which come on within seconds, minutes, or hours after ejaculation, can include extreme fatigue, muscle weakness, feverishness and sweating, mood disturbances and irritability, plus memory difficulties, concentration lapses, and incoherent speech.
According to a new review of POIS by researchers at Tulane University, this chronic disorder can induce these symptoms for up to a week after ejaculation, but despite how serious the effects are, there's still very little we know about the illness.
One of the reasons for that is because up until now there have been very few studies examining the condition, although POIS is recognised as a rare disorder by the National Institutes of Health Office of Rare Disease Research.
It's hoped that as more becomes known about the illness, more patients will seek evaluation and medical treatment – which in turn will tell us more about what's behind this unusual condition, which can affect men who ejaculate either through intercourse, masturbation, or even during wet dreams as they sleep.
Of course, the most obvious question is why are men with POIS experiencing these severe reactions at all after they ejaculate? According to the team from Tulane University, the leading hypothesis is one proposed by some of the Dutch scientists who first described the disease back in 2002.
"They postulated that POIS is an autoimmune or allergic disorder that generates an inflammatory reaction to a substance in the man's seminal fluid," the researchers write in their paper.
In short, it's thought that the men's own semen – or something that's contained within it – provokes some kind of allergic response when it comes into contact with other parts of the body, such as the skin.
Subsequent experiments using skin prick testing seemed to back this hypothesis up, with 29 of 33 POIS patients experiencing a skin reaction after being jabbed with their own harvested semen on their forearm – while placebos showed no such reaction.
Intriguingly enough, this line of enquiry could also hint at a potential hope of treatment for the condition.
In one study where two POIS patients received repeated injections of harvested semen with increasing concentrations over time, both men reported reduced symptoms after 15 and 31 months of treatment.
Of course, that explanation suggests the possibility that women too could conceivably be affected by an antigen in semen, and there has been at least one reported case of a woman experiencing POIS symptoms, although everything else we know about the condition comes from men presenting with the disorder.
Another hypothesis is that POIS might somehow result from chemical imbalances in the brain, with the aftermath of an orgasm producing symptoms similar to opioid withdrawal.
It's also worth noting that more than 50 percent of men with POIS in one study also experienced lifelong premature ejaculation, although the links between the two conditions aren't entirely clear.
While no treatments are currently available for POIS, future research could help solve some of the mysteries surrounding this unusual illness.
Many of those affected end up avoiding sexual activity for fear of the symptoms it could provoke – a devastating choice that would take an inevitable toll on lives, happiness, and prospects for relationships.
Here's hoping more science can shine a light on what's going on here, so people with POIS don't feel like they have to abstain from something that's supposed to make them feel great, not the opposite.
The findings are reported in Sexual Medicine Reviews.