Cluster headache is a type of severe, recurring pain that is located on one side of the head. It received its name from the clustering, or pattern, of frequent headaches that usually occur.

There are two main types of cluster headaches:

  • Episodic cluster headaches—These occur one or more times daily for multiple weeks. The headaches then go away and come back months or years later.
  • Chronic cluster headaches—These occur almost daily with headache-free periods lasting less than one month.

Either type of headache may switch to the other type.

The cause of cluster headaches is not known. It is thought that there is abnormal activation of the area of the brain that is responsible for regulating temperature, blood pressure, hormone release, and sleep. The pain is thought to be caused by a combination of widening of the blood vessels and inflammation of the nerves of the face.

Other possible causes include:

  • Alcohol use
  • Changes in barometric pressure
  • Changes in sleep pattern
  • Tobacco use
  • Medications, such as nitroglycerin