The Difference between people who tend to have a migraine headache and people who don’t is…

whether or not the blood vessel in the brain is easy to become wider.
 
The blood vessel is wound by the nerve which works as a sensor.
Normally there is a space between the blood vessel and the nerve.
In the case of migraine headache, the blood vessel becomes wider and stimulates the nerves winding around the blood vessel (Fig. 1).
The blood vessel is an artery so it is pulsating. That makes you feel pulsating pain in the head.
 
What makes the blood vessel wider?
 
(1) Weather
When the weather is nice, the blood vessel is contracted by proper atmospheric pressure. In this condition, there is no headache because the nerve is not stimulated. On the other hand, when the weather is bad, the atmospheric pressure lowers down, lowering the pressure in the head. That makes the blood vessel wider and stimulate the nerve, causing headache.
 
(2) Smell
The stimulation of strong smell such as cigarette’s smoke or perfume stresses the body. The brain is excited by the stress and increases the blood flow, making the blood vessel wider and causing headache.
 
(3) Too much sleeping
Usually when you sleep, the blood vessel gradually becomes wider by relaxation. But if you sleep too much, the blood vessel becomes too wide, causing headache.
 
(4) Hunger
When you feel hungry, your body tries to get more nutrition, widening the blood vessel and causing headache and irritation. So people who easily get angry tend to have migraine headache.
 
When there is a migraine headache, the blood vessel is wider so it is good to cool it down to shrink the blood vessel. Putting a cold towel on the area where you feel the headache is effective to alleviate the pain.