Headache

A headache is pain or discomfort in the head, scalp, or neck. Serious causes of headaches are rare. Most people with headaches can feel much better by making lifestyle changes, learning ways to relax, and sometimes by taking medicines.

Causes
The most common type of headache is tension headache. It is likely caused by tight muscles in your shoulders, neck, scalp, and jaw. A tension headache:

May be related to stress, depression, anxiety, a head injury, or holding your head and neck in an abnormal position.
Tends to be on both sides of your head. It often starts at the back of the head and spreads forward. The pain may feel dull or squeezing, like a tight band or vice. Your shoulders, neck, or jaw may feel tight or sore.
A migraine headache involves severe pain. It usually occurs with other symptoms, such as vision changes, sensitivity to sound or light, or nausea. With a migraine:

The pain may be throbbing, pounding, or pulsating. It tends to begin on one side of your head. It may spread to both sides.
The headache may be associated with an aura. This is a group of warning symptoms that start before your headache. The pain usually gets worse as you try to move around.
Migraines may be triggered by foods, such as chocolate, certain cheeses, or monosodium glutamate (MSG). Caffeine withdrawal, lack of sleep, and alcohol may also be triggers.
Rebound headaches are headaches that keep coming back. They often occur from overuse of pain medicines. For this reason, these headaches are also called medicine overuse headaches. People who take pain medicine more than 3 days a week on a regular basis can develop this type of headache.

Other types of headaches:

Cluster headache is a sharp, very painful headache that occurs daily, sometimes up to several times a day for months. It then goes away for weeks to months. In some people, the headaches never come back. The headache usually lasts less than an hour. It tends to occur at the same times every day.
Sinus headache causes pain in the front of the head and face. It is due to swelling in the sinus passages behind the cheeks, nose, and eyes. The pain is worse when you bend forward and when you first wake up in the morning.
Headaches may occur if you have a cold, the flu, a fever, or premenstrual syndrome.
Headache due to a disorder called temporal arteritis. This is a swollen, inflamed artery that supplies blood to part of the head, temple, and neck area.
In rare cases, a headache can be a sign of something more serious, such as:

Bleeding in the area between the brain and the thin tissue that covers the brain (subarachnoid hemorrhage)
Blood pressure that is very high
Brain infection, such as meningitis or encephalitis, or abscess
Brain tumor
Buildup of fluid inside the skull that leads to brain swelling (hydrocephalus)
Buildup of pressure inside the skull that appears to be, but is not a tumor (pseudotumor cerebri)
Carbon monoxide poisoning
Lack of oxygen during sleep (sleep apnea)
Problems with the blood vessels and bleeding in the brain, such as arteriovenous malformation (AVM), brain aneurysm, or stroke