Cluster headache is a primary headache characterized by intense blast-like headache attacks on one side of the orbit, behind the eye, and in the frontotemporal region, with ipsilateral conjunctival congestion, tearing, and nasal congestion. The headache occurs in clusters, with each cluster lasting from a few weeks to a few months before going into remission. It is more common in males, with a male to female ratio of 6:1, and is most common in young adults, with an age of onset of 20 to 50 years, but also in adolescents or older adults. The headache may start with a burning sensation next to the nose or pressure behind the eyes, and within minutes it rapidly develops into severe pain around the eyes and spreads to the frontotemporal, maxillary or ipsilateral whole head and neck. The headache is severe, colic, sharp pain, burning pain, etc., accompanied by flushing of the face, bulbar conjunctival congestion, tearing, nasal congestion, runny nose, etc. The patient is irritable, behaves manically, and is unable to sleep quietly. The duration of each pain episode ranges from 15 to 180 minutes, with an average of 45 minutes. The headache has distinct clusters of episodes and periods of pain relief that tend to occur in the spring and/or fall, with each cluster lasting 3 to 6 weeks, followed by a longer period of relief. During cluster attacks, the frequency of headache attacks is at least once a week and as often as several times a day. The headache attacks tend to be relatively constant and of similar duration, with most patients having headaches at night and about half of the patients experiencing waking up during sleep. Alcohol consumption and nitroglyceride use during attacks can provoke headaches, whereas these factors do not induce headaches during remission.