A cluster headache is a type of headache that is short-lasting, one-sided and very severe. It occurs in short groups or "clusters" and can cause symptoms such as red eyes, facial swelling, runny nose, drooping eyelids and decreased pupil size on the same side of the head where the pain occurs.

The cause of cluster headache is not yet fully known, but it appears to occur due to abnormal nervous system functioning. Although it is generally rare, it is more commonly seen in men over 30 years of age and who frequently consume alcohol.

If you suspect you may have a cluster headache, you are advised to consult a neurologist. Although there is no cure for this condition, treatment may involve oxygen therapy during flare-ups as well as medication like verapamil or lithium to prevent pain from returning.

Common symptoms

The main symptoms of a cluster headache are:

Intense headache
Red and/or watery eyes
Facial swelling
Runny or stuffy nose
Drooping of one eyelid
Small pupil in one eye

It is common for cluster headache pain to be located behind the eye and to be felt on one side of the head. This headache can appear with other symptoms, such as watery eyes or facial swelling. Read more about the different types of headaches and how they can present.

Symptoms can last between 15 minutes and 3 hours, and can return up to 8 times a day in some people, especially at night, for a period ranging from weeks to months. After this period, the person may remain symptom-free for a long time.

Confirming a diagnosis

A cluster headache diagnosis is usually confirmed by a neurologist based on the characteristics of the headache, like its intensity, frequency, location and duration. The doctor will also evaluate any related symptoms.

Sometimes, the doctor may also order imaging tests, such as an MRI or CT scan, to check for any abnormalities that may be causing the headache.

Possible causes

Cluster headaches are thought to be caused by abnormalities in the functioning of the hypothalamus, parasympathetic nervous system, and blood vessels in the the brain. However, it is not known for sure what causes these changes and how they lead to the development of symptoms.

In addition, cluster headaches are more common in men over 30 years of age who consume alcohol frequently, and/or have a history of head trauma, brain surgeries, or close family members with this type of headache.

Treatment options

Cluster headaches can be treated with inhalation of 100% oxygen, or with medication, such as sumatriptan or zolmitriptan in the form of an injection or nasal spray, to control symptoms during the attack.

In addition, medications such as verapamil, lithium, valproic acid and prednisolone may also be prescribed to prevent the headache from returning in some cases. These should be taken as prescribed.