What causes 'brain freeze' after cold food?

Answer

Researchers think rapid blood vessel changes irritate nerves. The exact mechanism is still debated.

Context

Brain freeze, formally called a cold-stimulus headache or ice cream headache, typically begins within seconds of cold food or drink touching the palate or the back of the throat and fades within a minute or two. The pain is felt in the forehead or temples, not in the mouth, an example of referred pain in which the brain misassigns the source of a signal that arrives via the trigeminal nerve.

The leading explanation involves blood vessels. A 2012 study using ultrasound on volunteers who held ice water against the palate reported a rapid rise in blood flow through the anterior cerebral artery followed by constriction of the vessel, and the pain peaked around the time of the dilation. This supports the idea that the artery's quick changes irritate nearby nerves, though a smaller study by other researchers found changes in a different artery, and some earlier work suggested constriction instead.

Because of these mixed findings, the mechanism is still debated. Researchers have also noted that people prone to migraine seem more likely to experience cold-stimulus headaches, which has made brain freeze a model for studying headache pathways. Taking a cold treat slowly, which lessens how quickly the palate cools, is associated in studies with fewer episodes, though this describes observations and is not meant as advice.