What causes brain freeze?
A rapid temperature change on the roof of the mouth, producing pain that the brain misattributes to somewhere else entirely.
The technical name is sphenopalatine ganglioneuralgia. When something very cold touches the palate — ice cream, a frozen drink — the blood vessels there constrict sharply, then dilate again as warmth returns. That rapid dilation is detected by nearby pain receptors.
The key structure is the trigeminal nerve, which carries sensation from the face and much of the head. The nerve endings in the palate share pathways with those serving the forehead and temples. When the brain receives the pain signal it cannot localise it precisely, and interprets it as coming from the forehead. This is referred pain, the same mechanism that makes a heart attack feel like arm pain.
The timing is characteristic: onset within a few seconds of the cold hitting the palate, peak at around 20 to 60 seconds, and resolution shortly afterwards. It is harmless.
The fixes follow directly from the mechanism. Press your tongue flat against the roof of your mouth to warm it. Drink something warm, or even room-temperature water. Breathe through your mouth with your tongue against the palate.
Prevention is simply eating cold things more slowly and keeping them toward the front of the mouth rather than against the palate.
An intriguing research angle: people who get migraines appear more likely to experience brain freeze, and it has been used deliberately in studies as a safe, repeatable way to trigger and observe head pain — one of the few pain responses researchers can induce ethically on demand.
Not everyone experiences it; susceptibility varies considerably.