Brain freeze, also known as ice cream headache or sphenopalatine ganglioneuralgia (SPG), occurs when something cold touches the roof of your mouth, resulting in a sudden, intense headache. While the exact mechanism isn't fully understood, it's believed to involve the rapid cooling and subsequent dilation of blood vessels in the roof of the mouth and the nearby sinuses. When the cold stimulus is removed, the blood vessels quickly constrict, causing pain.

The trigeminal nerve, which is responsible for sensations in the face, including pain, is thought to play a role in triggering brain freeze. When something cold is consumed, it may stimulate this nerve, leading to the sensation of pain.

Interestingly, researchers have found that warming the roof of the mouth after brain freeze can alleviate the pain, suggesting that the rapid temperature change may be a key factor in its occurrence.

Overall, while brain freeze can be uncomfortable, it's typically harmless and resolves on its own within a few seconds to a minute.