Cluster headache is a rare and very painful type of headache that usually occurs in periods of frequent attacks known as clusters. The pain is usually one-sided and can be described as burning, sharp, stabbing, or steady. Common symptoms during a cluster headache include:

• Extreme sharp or stabbing pain, usually in, behind or around one eye.
• The pain can spread to other areas of the face, head, and neck.
• Pain on one side of the head in a single cluster. Pain can switch to the other side in another cluster.
• Restlessness.
• A lot of tears.
• Redness of the eye on the side that hurts.
• Stuffy or runny nose on the side that hurts.
• Forehead or facial sweating.
• Skin color changes on the side of the face that hurts.
• Swelling around the eye on the side that hurts.
• Drooping eyelid on the side that hurts.

Cluster periods usually last for several weeks to months, and each cluster period may start at about the same time of year and last about the same length of time. The exact cause of cluster headaches is unknown, but they seem to be related to the bodys sudden release of histamine or serotonin in the area of a nerve in the face called the trigeminal nerve. The following may trigger cluster headaches:

• Alcohol use or smoking cigarettes.
• Change to a high altitude.
• Bright light.
• Exercise or exertion.
• Heat, either weather or a bath.
• Foods that contain nitrates, such as bacon or lunch meat.
• Cocaine use.

Cluster headaches can be diagnosed by a doctor based on the descriptions of the headache attacks and after other conditions have been ruled out. Although there is no cure for cluster headaches, treatments can help reduce the frequency and severity of attacks.