Brain freeze
Brain freeze, cold headache, ice cream headache,  shakeache, frigid face, freezie, Frozen Brain Syndrome, cold-stimulus headache, or its given scientific name sphenopalatine ganglioneuralgia are terms used to describe a form of cranial pain or headache which people are known to sometimes experience after consuming cold beverages or foods such as ice cream, slurpees, or margaritas, particularly when consumed quickly.

# Mechanism and cause
The reaction can sometimes be triggered within a few seconds after a very cold substance consumed comes into contact with the roof of the mouth. The pain is not caused by the cold temperature alone, rather quick warming of the hard palate. Letting the mouth slowly adjust back to normal temperatures can prevent this from occurring. Brain freeze is often a result of speaking or breathing out of the mouth after consuming something cold. The body's response to cold environments is to vasoconstrict the peripheral vasculature (to reduce the diameter of blood vessels).  This vasoconstriction is in place to reduce blood flow to the area, and thus minimize heat loss to keep warmth in the body.  After vasoconstriction, they return to normal status and artery size results in massive dilation (vasodilation) of the arteries that supply the palate (descending palatine arteries). The nerves in the region of the palate (greater and lesser palatine nerves) sense this as pain and transmits the sensation of this pain back to the trigeminal ganglia. This results in pain that is referred to the forehead and below the orbit, and other regions from which the trigeminal nerve receives sensation. (This phenomenon is similar to the pain that is present in the left arm when someone is having a myocardial infarction or heart attack). A similar effect occurs when one takes a prescription vasodilator, such as Nitroglycerin or Viagra. It is a stabbing or aching type of pain that usually recedes within 1020 seconds after its onset, but sometimes 3060 seconds, and can persist for up to five minutes in rare cases.  The pain is usually located in the midfrontal area, but can be unilateral in the temporal, frontal, or retro-orbital regions.
It has been reported that the pain can be relieved by moving the tongue to the roof of the mouth, which will cause greater warmth in the region; it is also believed that the pain can be relieved by slowly sipping room temperature water. Laying the head to the side may also provide relief. Creating a mask with one's hands placed over the mouth and nose while breathing rapidly is also said to be useful since the temperature in the mouth rises quickly.
A report was submitted to the British Medical Journal on brain freeze; it focused on the effect of speed of consumption of ice cream on causing brain freeze. Commonly referred to as "ice cream headaches," it has been studied as an example of referred pain, an unpleasant sensation localized to an area separate from the site of the painful stimulation.
It has been estimated that "30% of the population" experiences brain freeze or freeze head from ice cream. Some studies suggest that brain freeze is more common in people who experience migraines. Raskin and Knittle found this to be the case, with brain freeze occurring in 93% of migraine sufferers and in only 31% of controls. However, other studies found that it is more common in people without migraines. These inconsistencies may be due to differences in subject selectionthe subjects of the first study were drawn from a hospital population, whereas the controls in the second were student volunteers, making the tests inconclusive.