What causes brain freeze, and is it dangerous?

Brain freeze, also called ice cream headache, happens when something very cold touches the roof of the mouth or the back of the throat. It produces a brief, sharp pain in the forehead or temples. Doctors call it a cold-stimulus headache, and it is harmless. You do not freeze brain cells. The precise mechanism is still uncertain, though sensory nerves and blood vessels in the palate both seem to be involved. [1] [2] [3]

According to UCLA Health, the pain arrives suddenly, peaks in roughly 10 to 20 seconds and is usually gone within a minute or two. Harvard Health says it typically disappears within 30 seconds. The International Headache Society classifies it as a headache caused by eating, drinking or inhaling something very cold. The pain is felt in the forehead or temples and sometimes around the eyes, even though the cold is in the mouth. This mismatch is called referred pain, in which the brain misplaces the source of a signal because several neural pathways overlap. [1] [4] [3]

The older and widely repeated explanation centres on blood vessels. Johns Hopkins' Wojtek Mydlarz describes the palate's vessels constricting as a reflex to protect core temperature, then rapidly dilating, with the rebound sending a pain signal along the trigeminal nerve. Mayo Clinic's Dr. Starling and the Cleveland Clinic give similar accounts of vessels changing size and activating pain receptors. Harvard Health describes narrowing in the mouth triggering dilation of brain arteries, while noting the exact mechanism is unclear. [2] [5] [6] [4]

A more recent hypothesis, described by UCLA Health, shifts the focus to the sensory nerves of the roof of the mouth, branches of the trigeminal nerve, which are now suspected to be the main drivers, with blood flow possibly playing a part. Adam Taylor of Lancaster University writes that the simple story of vessels narrowing and then widening is probably too tidy. He cites a study that used ice water to trigger brain freeze and recorded changes in blood-flow velocity in an artery supplying the brain, and other experiments showing circulation changes. Current research points to an interaction between nerve signalling and blood flow, but the precise mechanism remains uncertain, partly because the headache is so brief that it is hard to study. [1] [3]

Brain freeze is common. In one study of 618 people aged 17 to 63, just over half reported having had it. In a Canadian experiment with 145 schoolchildren given 100 ml of ice cream, about 27% of those who ate it in under five seconds developed brain freeze, compared with around 13% of those who took more than 30 seconds. In another study, 73% of people who got brain freeze said eating or drinking cold things more slowly reduced how often it happened or how intense it was. The Cleveland Clinic similarly advises avoiding sudden extreme temperature changes in the mouth and throat and consuming very cold items slowly. [3] [6]