Almost anything can cause a migraine to an individual. They are as varied as the individuals they bother.

Allergies...a new toothpaste or someone else's deodorant.... Noise and lights (fluorescents are the worst!).... poor pillow and mattress... having a jaw off from a simple bumping....

Nearly every one of the migraine med companies have free a booklet to help you keep track and try to find what is causing your migraines. They will also do monthly/quarterly mailings with updates and more information.

What they suspect as to WHY the pain in the head: the blood vessels open wide and large amounts of blood flows to the brain. Caffeine constricts blood vessels, so it surely could help some people.