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It’s a hot afternoon, and the milkshake is perfect. You take a long, eager pull through the straw. Then it hits, a sharp, stabbing ache behind your forehead that makes you squeeze your eyes shut.
A few seconds later, it’s gone. Brain freeze is one of the most common pains people experience, but for a long time, nobody knew exactly what caused it.
Ice water through a straw
In 2012, a team led by Jorge Serrador of Harvard Medical School, working with researchers at the Department of Veterans Affairs and the National University of Ireland Galway, set out to catch brain freeze in the act.
They recruited 13 healthy adults and had them sip ice water through a straw pressed against the roof of their mouth, which is the ideal setup for triggering brain freeze. For comparison, the volunteers also sipped water at room temperature.
The researchers used transcranial Doppler, an ultrasound technique that measures blood flow through the skull, to track several arteries in the brain. Volunteers raised a hand when the pain started, and again when it stopped.
A blood vessel that widens, then tightens
The results pointed to one blood vessel, the anterior cerebral artery. It runs along the middle of the brain, roughly behind the eyes.
When the brain freeze began, this artery widened quickly, and blood flow through it rose sharply. Soon after, the artery narrowed again, and the volunteers’ pain faded.
Serrador’s team suggested a possible explanation. The skull is a closed, rigid container. A sudden rush of extra blood could briefly raise the pressure inside, and that pressure may be what causes the pain.
Why would the brain do this?
The researchers think the reaction may be a form of protection. The brain is sensitive to temperature and needs to keep working all the time. When something very cold hits the roof of the mouth, near major blood vessels, the body may respond by sending a rush of warm blood toward the brain to help keep it from cooling.
Then, before the pressure rises too far, the artery constricts again. As Serrador explained, this quick back-and-forth may help the brain stay warm without letting the pressure inside the skull build to dangerous levels.
Your brain can’t actually feel it
There’s another twist. The brain tissue itself has no pain receptors, which is why surgeons can operate on the brain of a patient who is awake.
Brain freeze pain is thought to be picked up by nerves in the coverings of the brain and around its blood vessels, particularly branches of the trigeminal nerve, a major nerve that carries sensation from the face and head. Because these nerves serve a wide area, the brain can’t tell exactly where the problem is. Instead of feeling cold in the roof of the mouth, you feel pain in your forehead or temples, an effect called referred pain.
That’s also why brain freeze has an official medical name, sphenopalatine ganglioneuralgia, after a cluster of nerves near the back of the nose and the roof of the mouth.
Slowing down really helps
Eating fast makes brain freeze more likely. In a 2002 study published in the BMJ, Canadian researchers randomly asked 145 middle school students to eat ice cream either quickly or slowly. About 27 percent of the fast eaters got brain freeze, compared with about 13 percent of the slow eaters.
If brain freeze does strike, warming the roof of your mouth can help it pass faster. Pressing your tongue against your palate or sipping something at room temperature are both commonly recommended, since they help bring the temperature back up.
A clue to bigger headaches
The researchers weren’t just curious about ice cream. People who get migraines are more likely to experience brain freeze than people who don’t, which suggests the two may share some underlying mechanisms.
Most headaches are hard to study, because they come on unpredictably and often last hours. Brain freeze can be triggered on demand and stops within seconds, so researchers can watch an entire headache from start to finish. As the University of Galway explained, the team hoped this could eventually help lead to new treatments for migraines and other headaches.
The study was small, and it was presented as a conference abstract rather than published as a full paper. Larger studies are needed to confirm the findings. But it offered one of the clearest looks yet at what’s happening during that brief, sharp pain, and the answer turned out to be blood flow, not your brain freezing.
