Three spoonfuls of ice cream in, scarfing it down like there’s no tomorrow. And suddenly: an icy jolt rips through your forehead, like someone just drove a sliver of ice straight between your eyes. It lasts ten, maybe twenty seconds tops, but in that moment you’d swear someone’s drilling into your skull. Here’s the funny part: scientists still haven’t fully agreed on what actually causes the famous brain freeze. Officially, it’s known as a “headache attributed to ingestion or inhalation of a cold stimulus.”
Suspect number one: an oversensitive nerve
The leading theory points to the trigeminal nerve, the main cable carrying pain and temperature signals from your face and mouth to your brain. Your mouth’s roof gets chilled fast, like when you wolf down ice cream or a slushie without pausing. That cold jolt seems to fire up this nerve’s fibers all at once. There’s also a variant of the theory involving the sphenopalatine ganglion, a cluster of nerves tucked just behind your nose. This ganglion may also get swept up in the cold shock.
Suspect number two: an artery that over-dilates
For years the go-to explanation was purely about blood vessels. The ones in your mouth and sinuses clamp down fast from the cold, then snap back open just as quickly, and that whiplash is what hurts. A 2012 study presented at the Experimental Biology conference, with researchers from Harvard involved, took it further. Using transcranial Doppler imaging, they found brain freeze coincides with a sudden dilation of the anterior cerebral artery, flooding the brain with blood all at once. That sudden rush of blood flow is what may trigger the pain signal. The study was small — just 27 people — so it counts as a solid lead, not the final word.
The theory gaining ground now is that there’s no single culprit. Nerves and blood vessels are likely acting together, feeding off each other, which would explain why the pain flares up and vanishes so fast and why it’s such a nightmare to study in a lab. After all, it’s hard to analyze something that’s gone in twenty seconds.
Does it have anything to do with migraines?
Here the science gets a little tangled. One study of 669 women found something striking. Those who’d had a migraine in the past year were twice as likely to get a headache after drinking ice-cold water. But a 1992 experiment found the opposite. People with migraines were actually less likely to get brain freeze, not more. To add to the confusion, a 2020 study with over 8,000 people found no difference in how often it happened. Still, it noted that when it did strike people with migraines, the pain tended to be more intense. So yes, there’s a link — nobody’s just managed to fully explain it yet.
So how do you avoid brain freeze?
It’s extremely common. In a survey of over 8,000 teenagers, 41% said they’d experienced brain freeze at some point. In a separate study with adults, the figure was around half. The practical advice, born more from common sense than a definitive clinical trial, is simple. Eat or drink your ice cream slowly. The faster the cold hits the back of your palate, the faster whatever mechanism is behind this kicks in. It doesn’t much matter which exact mechanism is to blame. If you feel the jolt coming on, pressing your tongue against the roof of your mouth or sipping something lukewarm usually stops it cold.
So next time a scoop of ice cream leaves you wincing mid-summer, take comfort in one thing: even science doesn’t have the final answer. At the very least, you’ve now got a great excuse to eat your next cone a little slower. If these odd little body glitches fascinate you, check out ACHOO syndrome, the reflex that makes some people sneeze just from looking at the sun. You can read the full science rundown on brain freeze at BBC Science Focus.