Postorgasmic illness syndrome (POIS) is a syndrome in which people have chronic physical and cognitive symptoms following ejaculation. The symptoms usually onset within seconds, minutes, or hours, and last for up to a week. The cause and prevalence are unknown; it is considered a rare disease. Signs and symptoms
The distinguishing characteristics of POIS are:

the rapid onset of symptoms after ejaculation;
the presence of an overwhelming systemic 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. Additional symptoms include headache, dizziness, lightheadedness, extreme hunger, sensory and motor problems, intense discomfort, irritability, anxiety, gastrointestinal disturbances, craving for relief, susceptibility to nervous system stresses (e.g. common cold), depressed mood, and difficulty communicating, remembering words, reading and retaining information, concentrating, and socializing. Affected individuals may also experience intense warmth or cold. An online anonymous self-report study found that 80% of respondents always experienced the symptom cluster involving fatigue, insomnia, irritation, and concentration difficulties.The symptoms usually begin within 30 minutes of ejaculation, and can last for several days, sometimes up to a week. In some cases, symptoms may be delayed by 2 to 3 days or may last up to 2 weeks.In some men, the onset of POIS is in puberty, while in others, the onset is later in life.
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.