According to one hypothesis, "POIS is caused by Type-I and Type-IV allergy to the males' own semen". Specifically,

POIS could also be caused by an auto-immune reaction not to semen itself, but to another substance that is released during ejaculation, such as to cytokines.

The allergy hypothesis has been disputed. According to one study, "IgE-mediated semen allergy in men may not be the potential mechanism of POIS".

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. While other causes have been proposed as well, none of the proposed causes seem to fully explain the disease.

These headaches are estimated to appear in roughly 1% of the population. They can occur with sexual activity at any age. It is more common in men than women, with studies putting the gender ratio between 1.2:1 and 3:1.

Erectile dysfunction from vascular disease is usually seen only amongst elderly individuals who have atherosclerosis. Vascular disease is common in individuals who have diabetes, peripheral vascular disease, hypertension and those who smoke. Any time blood flow to the penis is impaired, erectile dysfunction is the end result.

Hormone deficiency is a relatively rare cause of erectile dysfunction. In individuals with testicular failure like in Klinefelter syndrome, or those who have had radiation therapy, chemotherapy or childhood exposure to mumps virus, the testes may fail and not produce testosterone. Other hormonal causes of erectile failure include brain tumors, hyperthyroidism, hypothyroidism or disorders of the adrenal gland.

Structural abnormalities of the penis like Peyronie's disease can make sexual intercourse difficult. The disease is characterized by thick fibrous bands in the penis which leads to a deformed-looking penis.

Drugs are also a cause of erectile dysfunction. Individuals who take drugs to lower blood pressure, uses antipsychotics, antidepressants, sedatives, narcotics, antacids or alcohol can have problems with sexual function and loss of libido.

Priapism is a painful erection that occurs for several hours and occurs in the absence of sexual stimulation. This condition develops when blood gets trapped in the penis and is unable to drain out. If the condition is not promptly treated, it can lead to severe scarring and permanent loss of erectile function. The disorder occurs in young men and children. Individuals with sickle-cell disease and those who abuse certain medications can often develop this disorder.

Pelvic floor dysfunction can be an underlying cause of sexual dysfunction in both women and men, and is treatable by physical therapy.

For some patients, the headaches may be related to general exertion. About 40% of patients with sexual headaches in one study also experienced headaches from non-sexual exertion. A pressor response to exercise has been suggested as a mechanism. For other patients, the pain appears to be specifically activated by sexual excitement and contraction of facial and neck muscles.

Sporadic case studies have linked sexual headaches to the use of certain drugs, including amiodarone, pseudoephedrine, birth control pills, and cannabis. It may be secondary to another condition, such as reversible cerebral vasoconstriction syndrome. It is associated with migraines.

Cognitive behavioral therapy is the mainstay of treatment. At other times counseling, anti-anxiety and antidepressant medications have been shown to be of use.

Young males are most often affected, though similar symptoms have been reported in females with excessive vaginal discharge or leucorrhea, which is also considered a "vital fluid".

Premature ejaculation and impotence are commonly seen. Other somatic symptoms like weakness, easy fatiguability, palpitations, insomnia, low mood, guilt and anxiety are often present. Males sometimes report a subjective feeling that their penises have shortened. These symptoms are usually associated with an anxious and dysphoric mood state.

There is increasing evidence that the harmful products of tobacco smoking may damage the testicles and kill sperm, but their effect on male fertility is not clear. Some governments require manufacturers to put warnings on packets. Smoking tobacco increases intake of cadmium, because the tobacco plant absorbs the metal. Cadmium, being chemically similar to zinc, may replace zinc in the DNA polymerase, which plays a critical role in sperm production. Zinc replaced by cadmium in DNA polymerase can be particularly damaging to the testes.

Pre-testicular factors refer to conditions that impede adequate support of the testes and include situations of poor hormonal support and poor general health including:

- Hypogonadotropic hypogonadism due to various causes

- Obesity increases the risk of hypogonadotropic hypogonadism. Animal models indicate that obesity causes leptin insensitivity in the hypothalamus, leading to decreased Kiss1 expression, which, in turn, alters the release of gonadotropin-releasing hormone (GnRH).

- Undiagnosed and untreated coeliac disease (CD). Coeliac men may have reversible infertility. Nevertheless, CD can present with several non-gastrointestinal symptoms that can involve nearly any organ system, even in the absence of gastrointestinal symptoms. Thus, the diagnosis may be missed, leading to a risk of long-term complications. In men, CD can reduce semen quality and cause immature secondary sex characteristics, hypogonadism and hyperprolactinaemia, which causes impotence and loss of libido. The giving of gluten free diet and correction of deficient dietary elements can lead to a return of fertility. It is likely that an effective evaluation for infertility would best include assessment for underlying celiac disease, both in men and women.

- Drugs, alcohol

- Strenuous riding (bicycle riding, horseback riding)

- Medications, including those that affect spermatogenesis such as chemotherapy, anabolic steroids, cimetidine, spironolactone; those that decrease FSH levels such as phenytoin; those that decrease sperm motility such as sulfasalazine and nitrofurantoin

- Genetic abnormalities such as a Robertsonian translocation

Treatment is often with NSAIDs and antibiotics however, this is not always effective.

MOH is known to occur with frequent use of many different medications, including most commonly: triptans, ergotamines, analgesics, opioids. The underlying mechanisms that lead to the development of the condition are still widely unknown and clarification of their role is hampered by a lack of experimental research or suitable animal models. Various pathophysiological abnormalities have been reported and they seem to have an important role in initiating and maintaining chronic headache (genetic disposition, receptor and enzyme physiology and regulation, psychological and behavioural factors, physical dependencies, recent functional imaging results).

As of 2013 tension headaches affect about 1.6 billion people (20.8% of the population) and are more common in women than men (23% to 18% respectively). Despite its benign character, tension-type headache, especially in its chronic form, can impart significant disability on patients as well as burden on society at large.

Ophthalmodynia periodica is also referred to as "ice-pick headache", "needle-in-the-eye syndrome", and "sharp short-lived head pain." Ophthalmodynia periodica is considered a primary headache disorder, so it is not caused by any other conditions. Another well-known name for ophthalmodynia periodica is "jabs and jolts syndrome."

Orchialgia is long-term pain of the testes. It is considered chronic if it has persisted for more than 3 months. Orchialgia may be caused by injury, infection, surgery, cancer or testicular torsion and is a possible complication after vasectomy. IgG4-related disease is a more recently identified cause of chronic orchialgia.

One author describes the syndromes of chronic testicular pain thus:"The complaint is of a squeezing deep ache in the testis like the day after you got kicked there, often bilateral or alternating from one side to the other, intermittent, and, most commonly, associated with lower back pain. Sometimes it feels like the testicle is pinched in the crotch of the underwear but trouser readjustment does not help. There may also be pain in the inguinal area but no nausea or other symptoms. Back pain may be concurrent or absent and some patients have a long history of low back pain. Onset of pain is commonly related to activity that would stress the low back such as lifting heavy objects. Other stresses that might cause low back pain are imaginative coital positions, jogging, sitting hunched over a computer, long car driving, or other such positions of unsupported seating posture that flattens the normal lumbar lordosis curve."

Ophthalmodynia periodica does not have a confirmed cause, being a primary headache, but can be identified with other primary conditions. "As many as 40% of all individuals with ice pick headaches have also been diagnosed as suffering with some form of migraine headache."

The prevalence of migraine and vertigo is 1.6 times higher in 200 dizziness clinic patients than in 200 age- and sex-matched controls from an orthopaedic clinic. Among the patients with unclassified or idiopathic vertigo, the prevalence of migraine was shown to be elevated. In another study, migraine patients reported 2.5 times more vertigo and also 2.5 more dizzy spells during headache-free periods than the controls.

MAV may occur at any age with a female:male ratio of between 1.5 and 5:1. Familial occurrence is not uncommon. In most patients, migraine headaches begin earlier in life than MAV with years of headache-free periods before MAV manifests.

In a diary study, the 1-month prevalence of MAV was 16%, frequency of MAV was higher and duration longer on days with headache, and MAV was a risk factor for co-morbid anxiety.

Medication overuse headache (MOH), also known as rebound headache usually occurs when analgesics are taken frequently to relieve headaches. Rebound headaches frequently occur daily, can be very painful and are a common cause of chronic daily headache. They typically occur in patients with an underlying headache disorder such as migraine or tension-type headache that "transforms" over time from an episodic condition to chronic daily headache due to excessive intake of acute headache relief medications.

MOH is a serious, disabling and well-characterized disorder, which represents a worldwide problem and is now considered the third-most prevalent type of headache. Population-based studies report the prevalence rate of MOH to be 1% to 2% in the general population, but its relative frequency is much higher in secondary and tertiary care.

Hypnic headaches are benign primary headaches that affect the elderly, with the average age of onset being 63 ± 11 years. They are moderate, throbbing, bilateral or unilateral headaches that wake the sufferer from sleep once or multiple times a night. They typically begin a few hours after sleep begins and can last from 15–180 min. There is normally no nausea, photophobia, phonophobia or autonomic symptoms associated with the headache. They commonly occur at the same time every night possibly linking the headaches with circadian rhythm, but polysomnography has recently revealed that the onset of hypnic headaches may be associated with REM sleep.

Lithium carbonate 200–600 mg at bedtime is an effective treatment for most patients but for those that can not tolerate Lithium, Verapamil, indomethacin or methylsergilide may be tried. Two patients have also responded to flunarizine 5 mg. It has also been shown that 1–2 cups of coffee or 100–200 mg of caffeine before bed can prevent hypnic headaches.

For diagnosis of hypnic headache syndrome, headaches should occur at least 15 times per month for at least one month. Included in the differential diagnosis of a new onset nighttime headaches in the elderly is drug withdrawal, temporal arteritis, Sleep apnea, oxygen desaturated, Pheochromocytoma, intracranial causes, primary and secondary neoplasms, communicating hydrocephalus, subdural hematoma, vascular lesions, migraines, cluster headaches, chronic paroxysmal hemicrania and hypnic headache. All other causes must be ruled out before the diagnosis of hypnic headache can be made.

The incidence of RCVS is unknown, but it is believed to be "not uncommon", and likely under-diagnosed. One small, possibly biased study found that the condition was eventually diagnosed in 45% of outpatients with sudden headache, and 46% of outpatients with thunderclap headache.

The average age of onset is 42, but RCVS has been observed in patients aged from 19 months to 70 years. Children are rarely affected. It is more common in females, with a female-to-male ratio of 2.4:1.

The direct cause of the symptoms is believed to be either constriction or dilation of blood vessels in the brain. The pathogenesis is not known definitively, and the condition is likely to result from multiple different disease processes.

Up to two-thirds of RCVS cases are associated with an underlying condition or exposure, particularly vasoactive or recreational drug use, complications of pregnancy (eclampsia and pre-eclampsia), and the adjustment period following childbirth called "puerperium". Vasoactive drug use is found in about 50% of cases. Implicated drugs include selective serotonin reuptake inhibitors, weight-loss pills such as Hydroxycut, alpha-sympathomimetic decongestants, acute migraine medications, pseudoephedrine, epinephrine, cocaine, and cannabis, among many others. It sometimes follows blood transfusions, certain surgical procedures, swimming, bathing, high altitude experiences, sexual activity, exercise, or coughing. Symptoms can take days or a few months to manifest after a trigger.

Following a study and publication in 2007, it is also thought SSRIs, uncontrolled hypertension, endocrine abnormality, and neurosurgical trauma are indicated to potentially cause vasospasm.

Most patients have persistent headaches, although about 15% will remit, and 8% will have a relapsing-remitting type. It is not infrequent for NDPH to be an intractable headache disorder that is unresponsive to standard headache therapies.

Chronic headache, or chronic daily headache (CDH), is classified as experiencing fifteen or more days with a headache per month. It is estimated that chronic headaches affect "4% to 5% of the general population". Chronic headaches consist of different sub-groups, primarily categorized as chronic tension-type headaches and chronic migraine headaches. The treatments for chronic headache are vast and varied. Medicinal and non-medicinal methods exist to help patients cope with chronic headache, because chronic headaches cannot be cured. Whether pharmacological or not, treatment plans are often created on an individual basis. Multiple sources recommend "multimodal treatment", which is a combination of medicinal and non-medicinal remedies. Some treatments are controversial and are still being tested for effectiveness. Suggested treatments for chronic headaches include medication, physical therapy, acupuncture, relaxation training, and biofeedback. In addition, dietary alteration and behavioral therapy or psychological therapy are other possible treatments for chronic headaches.

Over one million cases of acute salpingitis are reported every year in the US, but the number of incidents is probably larger, due to incomplete and untimely reporting methods and that many cases are reported first when the illness has gone so far that it has developed chronic complications. For women age 16–25, salpingitis is the most common serious infection. It affects approximately 11% of females of reproductive age.

Salpingitis has a higher incidence among members of lower socioeconomic classes. However, this is thought of being an effect of earlier sex debut, multiple partners, and decreased ability to receive proper health care rather than any independent risk factor for salpingitis.

As an effect of an increased risk due to multiple partners, the prevalence of salpingitis is highest for people age 15–24 years. Decreased awareness of symptoms and less will to use contraceptives are also common in this group, raising the occurrence of salpingitis.

About 65% of persons with CH are, or have been, tobacco smokers. Stopping smoking does not lead to improvement of the condition and CH also occurs in those who have never smoked (e.g. children); it is thought unlikely that smoking is a cause. People with CH may be predisposed to certain traits, including smoking or other lifestyle habits.