Cluster headaches are most common in middle-aged male smokers and are among the most painful of all headaches. The individual is often awaken 1 to 3 hours after sleep with the headache in its full-blown state. The headache lasts about 1 hour and attacks occur frequently over several days to weeks - thus their name "cluster". The headaches will then disappear for periods of months to years before returning. The pain in cluster headaches is deep, nonthrobbing and severe located behind the ear and may radiate to the forehead and temple regions. There is also tearing of the affected eye, nasal congestion, and nasal drip.
Smoking, alcohol ingestion and napping often precipitate attacks. Immediate administration of oxygen (100% at 7 liters for 15 minutes) has been shown to provide some relief. It has been suggested that immersing the hand in ice water to the point of pain and elevating the bed may also provide some relief.