It is one of the most severe primary headache syndromes, with very intense unilateral head and eye pain. The attacks last from 15 minutes to 3 hours and recur in series (“clusters”), often at the same time of day. They are accompanied by redness of the eye, tearing, nasal stuffiness or other non-painful symptoms on the side of the headache. The acute attack is treated with oxygen therapy, analgesics and triptans. Prophylactic treatment includes specific blood pressure medications, corticosteroids and, in the case of drug resistance, occipital nerve or wing palatine node blockade, pulsed radiofrequency therapy.