Cluster headaches can be very painful. They occur several times a day, start suddenly, and last for a limited time. The exact cause of cluster headaches remains unknown, though there are several theories.

Cluster headaches occur cyclically. A bout of regular attacks, known as a cluster period, can last a few days, weeks, or months. During remission periods, a person has no headaches.

Cluster headaches are not common, affecting about 1 in 1,000 people. Six out of 10 cases involve men, and most of these are people who smoke. The headaches usually start after the age of 20.

Keep reading to learn more about cluster headaches, including the symptoms, causes, and treatment methods.

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Here are some key points about cluster headaches.

  • Cluster headaches typically affect one side of the head and the area around the eyes. Symptoms may include a reddened eye on the affected side of the head and a stuffy nose.
  • In northern countries, they are more common during the fall.
  • They affect around 1 in 1,000 people and are more common in men than women.
  • A cluster headache often appears suddenly, lasts around 1 hour, then disappears.
  • During a cluster period, headaches happen frequently. During remission, there is no pain.

Symptoms of cluster headaches include intense pain that starts rapidly and usually without warning. The pain is continuous rather than throbbing. It may cause a stabbing, sharp, or burning sensation.

The pain typically starts around the eye and may radiate to other parts of the head, including the face, neck, and shoulders. Pain may be present in a temple or a cheek. It remains on one side of the head.

There may also be:

  • restlessness
  • redness, swelling, or watering in the eye on the side of the pain
  • stuffy, blocked, or runny nose on the same side as the pain
  • pale skin
  • facial sweating
  • small pupil size
  • drooping of the eyelid on the same side as the pain

The pain can wake a person up during the night, and it may occur at the same time each night.

Each cluster can last from 15 minutes to several hours, but not usually more than 1 hour. After an attack, the pain will be gone, but the person may feel very tired.

Timing

A cluster period usually lasts from 6–12 weeks. It often starts at the same time each month, especially during springtime or fall.

Cluster headaches are either:

  • Episodic cluster headaches: A series of searing headaches typically lasting from 1 week to 3 months. There is usually a 6–12-month period of remission with no pain after an episode. Then the cycle repeats itself.
  • Chronic cluster headaches: The cluster period can persist for several months, 1 year, or longer. Periods of remission are short, lasting around a month.

A cluster period may consist of:

  • daily occurrences, with symptoms appearing several times each day
  • one attack, lasting from 15 minutes to 3 hours
  • attacks that occur around the same time each day
  • attacks that are more likely at night

It is not clear exactly why cluster headaches occur.

Research shows that during an attack there is more activity in the hypothalamus, an area of the brain that controls body temperature, hunger, and thirst.

This area of the brain releases chemicals that cause blood vessels to widen, resulting in a greater blood flow to the brain. One theory was that this may cause the headaches. However, this theory has since been rejected.

Other theories relate to inflammatory factors and neurotransmitters. Unfortunately, as this condition is so rare, it is difficult to find larger sample sizes for studies. However, researchers also think there could be a genetic link relating to the cause of the condition.

Some triggers can cause episodes of cluster headaches, such as alcohol, a sudden rise in temperature, or exercising in hot weather. There are also links between cluster headaches and smoking, irregular sleep-wake cycles, and allergies.

There is currently no cure for cluster headaches, but drugs and therapies can reduce the incidence and severity of attacks, such as sumatriptan.

Treatment aims to relieve some of the symptoms, shorten the periods of headaches, and reduce their frequency.

Over-the-counter (OTC) pain medication such as aspirin or ibuprofen can be too slow to effectively reduce pain before the headache is over.

Medications and treatments for cluster headaches aim either to prevent them or to act quickly.

Fast-acting treatments

A study in 2015 provided clinical guidance on treating cluster headaches, including:

  • Inhaling 100% oxygen: Breathing in oxygen through a mask at 7–10 liters per minute could reduce symptoms within 15 minutes. It is not always practical to have an oxygen cylinder and regulator close at hand, but some small units are available. Oxygen therapy may only postpone symptoms, rather than alleviating them.
  • Injectable sumatriptan (Imitrex): Triptans are a class of drug that can treat migraine. Sumatriptan can treat migraine and cluster headaches. The adult dose is a 6-milligram (mg) injection. People with high blood pressure or heart disease should avoid this drug.
  • Dihydroergotamine: This is an effective pain reliever for some people. A medical professional will need to give an intravenous dose, but people can also inhale the medication. The inhaler form is effective but slower-acting.
  • Octreotide (Sandostatin): These are synthetic versions of somatostatin, a brain hormone. It is an effective treatment for cluster headaches that is safe for those with hypertension or heart disease.
  • Local anesthetic nasal drops: Lidocaine (Xylocaine) is an effective treatment for cluster headaches.
  • Surgery: This may be an option if drug treatments do not work, or if the person cannot tolerate the medications. The surgery could involve cutting part of the trigeminal nerve, which serves the area behind and around the eye.

Possible future treatments

Some new treatment options under investigation include:

  • Occipital nerve stimulation: This involves implanting a small device over the occipital nerve. It sends impulses via electrodes.
  • Deep brain stimulation: This involves implanting a stimulator in the hypothalamus to change the electrical impulses in the brain.

Preventive treatment

People with cluster headaches take short- and long-term medications. When each period of clusters is over, the short-term treatments stop but the long-term ones may continue.

Short-term drugs

People typically take short-term medications until one of the long-term medications start working.

Examples include:

  • Corticosteroids: These steroids suppress inflammation. They are a fast-acting, preventive drug that can help those with new symptoms or those who have long periods of remission and short cluster periods.
  • Ergotamine (Ergomar): This temporarily narrows blood vessels throughout the body. People can take the medication at night before going to bed, but should not mix with triptans. People should avoid using the drug over long periods or if they have poor circulation.
  • Anesthetic on the occipital nerve: Injecting anesthetic can numb this nerve, which is at the back of the head. As a result, pain messages that travel along the nerve pathway are blocked.

Long-term drugs

People may take long-term drugs throughout the cluster period, such as:

  • Calcium channel blockers: People take these during the cluster period and then gradually reduce the dose, although some people may need to use them long term. Side effects include constipation, tiredness, and swollen ankles. Regular heart monitoring is necessary for people taking high doses.
  • Lithium carbonate: This is a treatment for bipolar disorder that is also effective in preventing chronic cluster headaches. Side effects include increased urination, diarrhea, and tremor. Regular blood tests will check for possible kidney damage.
  • Anti-seizure medications: These drugs also offer effective long-term treatments for cluster headaches.

Inappropriately discarded drugs can harm people, animals, and the environment. It is essential to dispose of any unwanted medication safely. Read our guide on medication disposal here.

Since the causes of cluster headaches remain unclear, there are no proven lifestyle measures for preventing them.

Identifying and avoiding triggers for cluster headaches could reduce their frequency or severity. Possible triggers include:

  • alcohol
  • some medications, such as inhaled nitroglycerin
  • exercising in hot weather
  • sudden rises in body temperature
  • smoking
  • irregular sleep patterns

Cluster headaches and migraine are both severe forms of headache, but they are different and need specific treatments.

Before a migraine headache, a person will typically experience an “aura,” or visual disturbances, including flashing lights or zigzag lines. Migraine can last for up to 72 hours, and commonly involves nausea, vomiting, and sensitivity to light.

A cluster headache starts and ends suddenly, and it lasts a shorter time. It can feature congestion, watery eyes, and a runny nose. It normally affects only one side of the head, and the eye that is watering is on the same side.

A person with migraine prefers to lie down during an attack, but people with cluster headaches may find that lying down worsens the pain.

To discover more evidence-based information and resources for headache and migraine, visit our dedicated hub.

Risk factors for cluster headaches include:

  • being male
  • being older than 30
  • drinking alcohol
  • prior experience of brain surgery or trauma
  • family history of cluster headaches or migraine headaches

Anyone who has regular headaches should see a doctor. Treatment can relieve symptoms, and it may be necessary to rule out any possible underlying causes.

Vagus nerve stimulation may also be effective.

Learn more about vagus nerve stimulation here.

Cluster headaches are painful headaches that can occur several times a day. Episodes typically come in cycles and may occur around the same time each year.

The symptoms of cluster headaches include sharp, stabbing pain on one side of the head. There can also be restlessness, nasal congestion, and pale skin.

There is currently no cure for cluster headaches. However, people can take a combination of short- and long-term medications to reduce the frequency and severity of episodes.