A migraine is a headache disorder that is characterized by recurrent headaches that are moderate to severe. Most of the time, the headaches affect one half of the head, are pulsating in nature, and last from a few hours to several days. Associated symptoms may include light sensitivity, nausea, and vomiting. The pain is generally made worse by physical activity. Up to one-third of people affected have an aura: a visual disturbance that signals that the headache will soon begin (prodrome). Occasionally, an aura can occur with little or no headache following it.