2.1
Cluster headaches are characterised by episodes of unilateral periorbital pain, conjunctival injection, lacrimation and rhinorrhoea. Attacks can last from a few minutes to several hours and can occur many times a day, for several days, weeks, months or years. Migraines are severe headaches that may last for hours, days or longer, often accompanied by nausea, photophobia, phonophobia and the perception of unpleasant odours. In some people migraines may be accompanied by an aura, characterised by the focal neurological symptoms that usually precede or sometimes accompany the headache. The International Headache Society's International Classification of Headache Disorders classifies migraine types.