Here is a copy of my write up on migraines:

Migraines start when the blood vessels around the brain constrict tightly, then rebound vasodilate leading to inflammation.

There can be multiple triggers including dietary amines, allergies, hormones, bright lights, etc.  So anyone suffering from migraines should keep a migraine log to look for their trigger so this can be addressed as well.  Anytime a migraine occurs list whatever was eaten, or drunk, what you were exposed to (fumes, pollen, etc.), if a woman is it near her menstrual cycle, bright lights, etc.

The best supplements for migraines are magnesium, kudzu, and coleus forskohlii.  Magnesium deficiencies are common and can lead to a host of problems, including frequent migraines.  Calcium causes blood vessels to contract, leading to the initial constriction.  Magnesium is a calcium antagonist, and relaxes blood vessels to help prevent the initial vasoconstriction.  For this reason the magnesium should be taken by itself, not with any calcium.  This includes with foods that may contain calcium.  Recommended dose is 300mg of magnesium malate twice daily, morning and afternoon, at least 30 minutes before ingesting any calcium sources. If you take a calcium/magnesium supplement this is best taken at night before bed.  If you cannot find magnesium malate then magnesium citrate is my second choice.  Avoid magnesium oxide since it is poorly absorbed and it burns the intestinal wall leading to inflammation and diarrhea.

Kudzu and coleus forskohlii are both vasodilators to help prevent the initial vasoconstriction. Recommended dose is 2 capsules of either herb 3 times daily before meals, and in addition at the first signs of an impending migraine.  Kudzu is preferred if there are hormonal imbalances. Forskohlii though is an excellent anti-inflammatory since it blocks both inflammatory prostaglandins and leukotrienes.