A migraine headache is a severe pain felt on one, and sometimes, both sides of the head. The pain is mostly in the front around the temples or behind one eye or ear. Besides pain, you may have nausea and vomiting, and be very sensitive to light and sound. Migraine can occur any time of the day, though it often starts in the morning. The pain can last a few hours or up to one or two days.

We don't know what causes migraine headaches, but some things are more common in people who have them.

Most often, migraine affects people between the ages of 15 and 55.

• Many people have a family history of migraine.

• They are more common in women.

• Migraine often becomes less severe and frequent with age.

What causes migraine?

One theory about the cause of migraine is the blood flow theory, which focuses on blood vessel activity in the brain. Blood vessels either narrow or expand. Narrowing can constrict blood flow, causing problems with sight or dizziness. When the blood vessels expand, they press on nerves nearby, which causes pain.

Another theory focuses on chemical changes in the brain. When chemicals in the brain that send messages from one cell to another, including the messages to blood vessels to get narrow or expand are interrupted, migraines can occur.

More recently, genes have been linked to migraine. People who get migraines may inherit abnormal genes that control the functions of certain brain cells. And something the person's body is sensitive to in some way triggers the actual headaches.

Headache triggers can vary from person to person. Most migraines are not caused by a single factor or event. Your response to triggers can also vary from headache to headache. Many women with migraine tend to have attacks brought on by:

• Lack of food or sleep.

• Bright light or loud noise.

• Hormone changes during the menstrual cycle.

• Stress and anxiety.

• Weather changes.

• Chocolate, alcohol, or nicotine.

• Some foods and food additives, such as MSG or nitrates.