Q: Ever get a ‘Brain Freeze’ while eating ice cream? Why does it happen? 
What can you do about it? Is it preventable?
A: Sensitive nerves located above the roof of the mouth may respond to the cold temperatures of ice cream with the dilation of blood vessels; this dilation, in turn, can cause a headache. This type of headache vanishes quickly, but to avoid it entirely, Dr. Jason Rosenberg (director of the Johns Hopkins Headache Center) recommends the following course of action:
1) consume ice cream slowly, or
2) before swallowing it, warm up the ice cream by holding it in the front of your mouth for a short time.
The latter method has the added benefit of allowing you to savor each bite (or lick) a moment longer.
Do It And How 