Not an ordinary headache

Cluster headache is a primary headache disorder, which means the headache is the condition itself rather than a symptom of something else. It is less common than migraine or tension headache, but it is widely recognized as one of the most painful conditions a person can experience. People who live with it often struggle to find words for the intensity, and many have had the frustrating experience of others assuming it is "just a bad headache."

The good news is that once cluster headache is correctly diagnosed, there are specific approaches that help many people during attacks and through cluster periods. This article explains what to look for and how to get the right help.

How an attack typically unfolds

• Severe one-sided pain, usually around or behind one eye, the temple or forehead. It is often described as boring, stabbing or burning.
• Fast onset. Pain builds to its peak within minutes.
• Short but intense duration, usually lasting from about 15 minutes to 3 hours if left without care.
• Symptoms on the same side as the pain, such as a red or watering eye, drooping eyelid, smaller pupil, runny or blocked nostril, facial sweating or flushing, and eyelid swelling.
• Restlessness. Unlike migraine, where people usually want to lie still, many people with cluster headache pace, rock or feel unable to stay still.
• Clockwork timing. Attacks often happen at the same time each day, frequently waking people an hour or two after falling asleep.

Episodic and chronic patterns

The name comes from the way attacks come in clusters. During a cluster period, which can last weeks to months, a person may have anywhere from one attack every other day to several a day. Many people find these periods return at similar times of year.

• Episodic cluster headache is the more common form. Cluster periods are separated by pain-free remissions lasting months or even years.
• Chronic cluster headache means attacks continue for a year or more without a meaningful break, or with only short breaks.

What seems to drive it

The exact cause is not fully understood. Research points to the hypothalamus, a part of the brain involved in the body's internal clock, which may explain the striking timing. The trigeminal nerve, which carries sensation from the face, and nearby blood vessels are also involved in producing the pain and the eye and nose symptoms.

During a cluster period, common triggers include:

• Alcohol, often bringing on an attack quickly
• Strong smells such as paint, solvents or perfume
• Becoming overheated
• Disrupted sleep or daytime naps
• High altitude

Smoking is common among people with cluster headache, and stopping is good for overall health, though it does not always change the headaches. Cluster headache is more frequently diagnosed in men, but it affects people of all genders.

How it differs from migraine

Cluster headache is sometimes mistaken for migraine, sinus problems or dental pain. Key differences: cluster attacks are shorter, always one-sided during an attack, come with eye and nose symptoms on that side, make people restless rather than still, and follow a clock-like pattern. Migraine attacks usually last longer, often bring nausea and sensitivity to light and sound, and make people want to rest in a dark room. Some people have both conditions.

Getting diagnosed

There is no single test for cluster headache. Diagnosis is based on the pattern of symptoms, so a detailed headache diary is extremely valuable. Record the time each attack starts and ends, which side is affected, the eye and nose symptoms, possible triggers, and what you tried. Your doctor may arrange a brain scan to rule out other causes, and may refer you to a neurologist or headache specialist.

Approaches a doctor may discuss

Because attacks are short and intense, standard over-the-counter painkillers usually act too slowly to help. Care for cluster headache tends to fall into three groups, which your doctor can explain in detail:

• Acute options to shorten an attack. High-flow oxygen through a face mask is a well-established option prescribed by doctors, and certain fast-acting prescription medicines are also used.
• Preventive options taken through a cluster period to reduce how often attacks happen.
• Short-term bridging options sometimes used at the start of a cycle while preventive medicine takes effect.

Some people are offered nerve blocks or devices that stimulate nerves. A specialist can talk through what suits your situation, including any heart or other conditions that affect which options are safe.

Practical steps during a cluster period

• Avoid alcohol completely while a cycle is active.
• Keep a regular sleep schedule and skip daytime naps if they seem to trigger attacks.
• Steer clear of strong smells and overheating where you can.
• Keep any prescribed attack plan close at hand, including at night.
• Tell family or housemates what an attack looks like, so they know what is happening and how to help.
• Let your employer know about likely absences or the need for flexibility during cycles.

Warning signs that need urgent care

Looking after your mental health

Cluster headache can be frightening and exhausting, and the dread of the next attack during a cycle is very real. Low mood and anxiety are understandable responses. Please talk to your doctor if you are struggling. If you ever have thoughts of harming yourself, call or text 988 in the US to reach the 988 Suicide & Crisis Lifeline, or your local emergency number elsewhere. Connecting with others who live with cluster headache can also be a powerful source of support and practical advice.

Bringing it together

Cluster headache causes short, severe, one-sided attacks with eye and nose symptoms, often at the same time each day and in repeating cycles. Getting an accurate diagnosis matters, because specific approaches such as prescribed oxygen and targeted medicines help many people. A headache diary, trigger awareness and a clear attack plan can make cluster periods more manageable.

Use our free Pain Check-Up to help describe your attacks to a doctor, and find others in the headache, head and eye pain groups.