What Are Cluster Headaches?

Cluster headaches are very painful headaches on one side of your head. They come in groups, or clusters. They usually happen over a few weeks to months. The headaches appear suddenly and are more common in men than in women. They cause extreme pain on one side of the head, along with a watery eye and stuffy nose on the same side. Cluster headaches are often so painful that you can't carry on with normal activities during the headache. The good news is, they don't cause permanent damage.

What Causes Them?

We don't know what causes cluster headaches. They may be partly genetic, since people whose parents, brothers, or sisters have cluster headaches are at more likely to get them. Cluster headaches may be caused by a problem in an area of the brain that seems to be more active in people who have cluster headaches.

If you are prone to cluster headaches, certain triggers may cause a headache or make one worse. These triggers often include: alcohol, sleep apnea (regularly stopping breathing during sleep), stress, fatigue, or certain medications that widen blood vessels, such as nitroglycerin or histamine.