Cluster headache is a rare neurological headache disorder that causes extremely severe pain on one side of the head, usually around or behind one eye. Attacks occur in groups or “clusters”, often at similar times each day for weeks or months.
Symptoms
Pain begins rapidly and usually lasts 15 minutes to three hours. On the painful side there may be a red or watering eye, blocked or runny nose, eyelid swelling, facial sweating or a drooping eyelid. People are often restless and unable to lie still.
Diagnosis
A clinician diagnoses cluster headache from its distinctive pattern and neurological examination. Brain imaging may be needed for a first episode, unusual features or an abnormal examination. A headache diary can record timing, duration and associated symptoms.
Treatment
Ordinary painkillers act too slowly. Effective acute treatments include high-flow oxygen through a suitable mask and a fast-acting triptan injection or nasal spray prescribed after assessment. Preventive treatment, commonly verapamil with heart monitoring, may be used during a cluster period. Alcohol can trigger attacks during an active cluster and is best avoided then.
When to seek urgent help
A first episode of severe one-sided headache needs prompt assessment. Call emergency services for a sudden “worst-ever” headache, weakness, speech difficulty, confusion, collapse, seizure, fever with neck stiffness, new vision loss or headache after a serious injury.
Sources
Reviewed: 28 August 2026