Causes

Research scientists are unclear about the precise cause of migraine headaches. There seems to be general agreement, however, that a key element is blood flow changes in the brain. It appears that migraine headache sufferers have a genetically predisposed defect that involves the brain chemical serotonin. This chemical regulates mood, sleep, and the narrowing and widening of blood vessels. This is what probably happens when you get a migraine: First of all an electrical wave sweeps over the brain. This electrical activity causes a surge in the serotonin level, which causes blood vessels to constrict. Reduced blood flow decreases the brain's supply of oxygen. Symptoms signalling a headache, such as distorted vision or speech, may then result, similar to symptoms of stroke. Serotonin seeps into the surrounding tissues lowering the level of serotonin in the brain. The blood vessels expand and the nerves in the brain become irritated by the lack of serotonin.
The electrical activity is brought on by a number of triggers.

Triggers for migraine headaches

• worry, stress ,anxiety, depression and anger
• drinking too much caffeine
• too much or too little sleep
• changes in weather and seasons
• missing a meal
• eating certain foods (e.g. chocolate, aged cheeses, citrus fruits pickled,
  fermented, or marinated foods, cured meats, aspartame, monosodium glutamate ).
• drinking alcohol (especially red wine)
• getting too much sun or overexposure to bright, glaring indoor lights.
• a change in altitude or pressure
• strong odours (perfume, cigarette smoke, paint, etc.)
• motion (in a car or boat)
• menstruation
• oral contraceptives
• oestrogen replacement therapy
• pregnancy