Tension headaches, also known as muscle-contraction headaches, are characterized by dull, constant pain, often on both sides of the head. A tension headache is often likened to the sensation of a tight band or vise squeezing the head. The pain is usually mild to moderate, and not incapacitating, and may be accompanied by tightness in the neck and shoulders. These headaches can last between four hours and a week.

Tension headaches are classified into two categories:

Episodic headaches
Chronic (daily) headaches

Migraine headaches are signaled by intense throbbing pain, which is usually one-sided, near an eye, and of moderate to severe intensity. The headaches, which can be disabling, can last up to 72 hours. Nausea and vomiting, sensitivity to light and sound, dizziness, and blurred vision often come with a migraine.

About 40% of migraine sufferers also experience an aura--in other words, warning signs such as flashing lights or dots--to signal an attack is coming.

Cluster headaches produce severe, sharp, stabbing pain, usually on one side of the head and centered around one eye. They are severely incapacitating. These headaches tend to occur in clusters of 1-4 a day for 4-8 weeks, last between 30 and 90 minutes each, and then disappear for months. Flushing of the face, tearing of the affected eye, and a stuffy or runny nose on the same side where the pain is located may occur during an attack. Cluster headaches are most frequent in the spring and fall.