Causes of headaches may include dehydration; fatigue; sleep deprivation; stress;[4] the effects of medications (overuse) and recreational drugs, including withdrawal; viral infections; loud noises; head injury; rapid ingestion of a very cold food or beverage; and dental or sinus issues (such as sinusitis).

The description of the headache and findings on neurological examination, determine whether additional tests are needed and what treatment is best.

While primary headaches may cause significant daily pain and disability, they are not dangerous from a physiological point of view.

Secondary headaches are caused by an underlying disease, like an infection, head injury, vascular disorders, brain bleed, stomach irritation, or tumors.

[15] Tension-type headaches usually present with non-pulsing "bandlike" pressure on both sides of the head, not accompanied by other symptoms.

[9][19] More serious causes of secondary headaches include the following:[11] Gastrointestinal disorders may cause headaches, including Helicobacter pylori infection, celiac disease, non-celiac gluten sensitivity, irritable bowel syndrome, inflammatory bowel disease, gastroparesis, and hepatobiliary disorders.

CVS is characterized by episodes of severe vomiting, and often occur alongside symptoms similar to those of migraine headaches (photophobia, abdominal pain, etc.).

These include the extracranial arteries, middle meningeal artery, large veins, venous sinuses, cranial and spinal nerves, head and neck muscles, the meninges, falx cerebri, parts of the brainstem, eyes, ears, teeth, and lining of the mouth.

Dilation of these extracranial blood vessels activates the pain receptors in the surrounding nerves, causing a headache.

Triptans, medications that treat migraines, block serotonin receptors and constrict blood vessels.

[37] Tension headaches are thought to be caused by the activation of peripheral nerves in the head and neck muscles.

[38] Cluster headaches involve overactivation of the trigeminal nerve and hypothalamus in the brain, but the exact cause is unknown.

These "red flag" symptoms mean that a headache warrants further investigation with neuroimaging and lab tests.

If 3 characteristics of POUND are present, migraine is 3 times more likely a diagnosis than tension type headache (likelihood ratio 3).

While mobile electronic diaries for smartphones are becoming increasingly common, a recent review found most are developed with a lack of evidence base and scientific expertise.

If there are signs of infection such as fever, rash, or stiff neck, a lumbar puncture to look for meningitis should be considered.

[citation needed] All people who present with red flags indicating a dangerous secondary headache should receive neuroimaging.

[14] Non-contrast computerized tomography (CT) scan is usually the first step in head imaging as it is readily available in Emergency Departments and hospitals and is cheaper than MRI.

[14] MRI is more sensitive for identifying intracranial problems, however it can pick up brain abnormalities that are not relevant to the person's headaches.

[14] The American College of Radiology recommends the following imaging tests for different specific situations:[53] A lumbar puncture is a procedure in which cerebral spinal fluid is removed from the spine with a needle.

Secondary headaches, according to the same classification system, can also be due to the injury of any of the facial structures including teeth, jaws, or temporomandibular joint.

In those with chronic headaches the long term use of opioids appears to result in greater harm than benefit.

Moderate to severe attacks should be treated first with an oral triptan, a medication that mimics serotonin (an agonist) and causes mild vasoconstriction.

It works by blocking the reuptake of serotonin and norepinephrine, and also reduces muscle tenderness by a separate mechanism.

Abortive therapy for cluster headaches includes subcutaneous sumatriptan (injected under the skin) and triptan nasal sprays.

[79] The first recorded classification system was published by Aretaeus of Cappadocia, a medical scholar of Greco-Roman antiquity.

[84] Just as in adults, most headaches are benign, but when head pain is accompanied with other symptoms such as speech problems, muscle weakness, and loss of vision, a more serious underlying cause may exist: hydrocephalus, meningitis, encephalitis, abscess, hemorrhage, tumor, blood clots, or head trauma.

In these cases, the headache evaluation may include CT scan or MRI in order to look for possible structural disorders of the central nervous system.

Drinking plenty of water throughout the day, avoiding caffeine, getting enough and regular sleep, eating balanced meals at the proper times, and reducing stress and excess of activities may prevent headaches.

[92] Cardiac cephalgia[93] is a rare type of headache occurring during myocardial infarction, characterized by sudden, severe head pain that typically develops during or immediately following a heart attack.