Migraine is recurrent vascular headache, usually on one side of the head. Severe throbbing pain is sometimes accompanied by nausea and vomiting. Some migraine patients have warning symptoms (an "aura") before the headache, including visual disturbance, weakness, numbness, or dizziness. If a stimulus (e.g., a particular food or drink) is found to trigger attacks, avoidance can prevent them. Drugs may be taken as an attack begins (to abort it) or daily by patients with very frequent attacks (to prevent them or reduce their severity).