Cluster headaches manifest as unilateral, severe pain, most prominently around the eye. A characteristic feature of the pain is its tendency to occur at night or in the early morning hours, often at the same time each day.

Accompanying symptoms include:

* Congestion, watering, or a burning sensation in the eye on the affected side
* Nasal congestion or runny nose on the affected side
* Sweating on the forehead or face on the affected side
* Drooping eyelid on the affected side
* Facial and periorbital edema (swelling)
* Agitation and restlessness
* The individual often experiences an increased restlessness, an inability to sit still, and a need to pace. Photophobia (light sensitivity) may also occur, as in migraine headaches.
* During an attack, bradycardia (slow heart rate), hypertension (increased blood pressure), and increased gastric acid secretion can occur.