If we eat too much of a cold substance, it cools our sinuses and the blood vessels called capillaries. These are really really small blood vessels. So our ears, our mouth, around our nose are affected. It isn’t our brain that freezes, it is more that the capillaries are constricting and then getting bigger again and it is this rapid process which can cause the freeze because they are getting cold really quick! The top of our mouth too, (called the palate) has a nerve which is close to pain receptors. When the blood vessels dilate there is this ‘background’ pain sensation sent from the top of the mouth to the brain. Did you know the scientific name for ‘brain freeze’ is sphenopalatine ganglioneuralgia! That is a long name.