It is  unknown whether there is a relationship between hypersexuality, pornography addiction, compulsive sexual behavior and POIS. Some evidence indicates that POIS patients have a history of excessive masturbation, suggesting that POIS could be a consequence of sex addiction. There is anecdotal evidence on porn addiction internet forums, that many men experience POIS like symptoms after ejaculation. Other possibilities
POIS could be caused by hyperglycemia or by chemical imbalances in the brain.Sexual activity for the first time may set the stage for an associated asthma attack or may aggravate pre-existing asthma. Intense emotional stimuli during sexual intercourse can lead to autonomic imbalance with parasympathetic over-reactivity, releasing mast cell mediators that can provoke postcoital asthma and / or rhinitis in these patients.It is also possible that the causes of POIS are different in different individuals. POIS could represent "a spectrum of syndromes of differing" causes.None of the proposed causes for POIS fully explain the connection between POIS and lifelong premature ejaculation. Diagnosis
There is no generally agreed upon diagnostic criteria for POIS. One group has developed five preliminary criteria for diagnosing POIS. These are:

POIS is prone to being erroneously ascribed to psychological factors such as hypochondriasis or somatic symptom disorder.An online survey study suggested that only a small number of self-reported POIS fulfill entirely the five criteria. This study proposed to change the Criterion 3 with “In at least one ejaculatory setting (sex, masturbation, or nocturnal emission), symptoms occur after all or almost all ejaculations.”

Management
There is no standard method of treating or managing POIS.
They may show up as restlessness, irritability, increased sexual frustration, apathy, sluggishness, neediness, dissatisfaction with a mate, or weepiness over the days or weeks after intense sexual stimulation. Such phenomena may be part of human mating physiology itself. Sexual headache is a distinct condition characterized by headaches that usually begin before or during orgasm. Mechanism
The cause of POIS is unknown. Some doctors hypothesize that POIS is caused by an auto-immune reaction. Other doctors suspect a hormone imbalance as the cause. Different causes have also been proposed. None of the proposed causes fully explain the disease. Allergy hypothesis
According to one hypothesis, "POIS is caused by Type-I and Type-IV allergy to the males own semen". This was conditioned by another study stating "IgE-mediated semen allergy in men may not be the potential mechanism of POIS".Alternatively, POIS could be caused by an auto-immune reaction not to semen, but to a different substance released during ejaculation, such as cytokines. Hormone hypothesis
According to another hypothesis, POIS is caused by a hormone imbalance, such as low progesterone, low cortisol, low testosterone, elevated prolactin, hypothyroidism, or low DHEA.POIS could be caused by a defect in neurosteroid precursor synthesis. If so, the same treatment may not be effective for all individuals. Different individuals could have different missing precursors leading to a deficiency of the same neurosteroid, causing similar symptoms. Withdrawal hypothesis
The majority of POIS symptoms like fatigue, muscle pains, sweating, mood disturbances, irritability, and poor concentration are also caused by withdrawal from different drug classes and natural reinforcers.