Heather L. knew a migraine was coming on within minutes. Her head began to pound on one side and waves of nausea washed over her. She ran into a windowless bathroom, swallowed two ibuprofen tablets, shut off the light, and huddled in a corner, eyes tightly closed. Thankfully, this one was short, just a few hours. By now Heather had learned precisely what to do. All it took was a strong shaft of sunlight into her room as she slept to trigger an attack.

Although migraine is considered a type of headache, it is actually a response to changes in the diameters of blood vessels in the face, head, and neck. Constriction followed by dilation of these vessels causes head pain (usually on one side), nausea and perhaps vomiting, and sensitivity to light. There are two variants--10 to 15% of sufferers experience classic migraine, which lasts 4 to 6 hours and is preceded by an aura of light in the peripheral vision. Common migraine usually lacks an aura but may last 3 to 4 days.

On a cellular level, abnormal levels of the neurotransmitter serotonin in the brain are thought to constrict the blood vessels that cause migraines. On a practical level, many sufferers link migraine attacks to eating a particular food (chocolate, red wine, nuts, and processed meats top the list), lack of sleep, excess stress, glaring lights, high altitude, and stormy weather.

Nearly all migraine sufferers can be helped. Over-the-counter pain relievers help some people, as do the prescription beta blockers and a drug called Imitrex. All of these constrict blood vessels in the head. Tricyclic antidepressant drugs also help by keeping serotonin available longer, thereby off-setting a deficit that may cause this painful disorder.