You take one eager bite of ice cream or a big slurp of a slushie, and then it hits: a sharp, stabbing ache right behind your forehead. You squeeze your eyes shut and wait. A few seconds later it's gone, as if nothing happened.
That's a cold-stimulus headache, better known as brain freeze or an ice-cream headache. It starts when something very cold touches the roof of your mouth. The leading explanation is that blood vessels there quickly tighten and then swell, and a major facial nerve sends a pain signal that your brain mistakes as coming from your forehead.
A Case of Mistaken Identity
Here's the step-by-step version scientists think happens. The cold rapidly chills tiny blood vessels called capillaries, and they constrict. As they warm back up, they swing the other way and widen dramatically.
Pain sensors in the roof of your mouth notice that sudden widening and send signals to the brain through the trigeminal nerve, one of the major nerves of the face. Because that nerve also carries pain from the face, the brain reads the signal as coming from the forehead. This is called referred pain, the same kind of mix-up doctors see with heart attacks.
Something similar but painless happens to your face on a chilly day. Capillaries tighten in the cold, then widen as you warm up, which is why your cheeks look flushed when you come back inside.
A Second Theory
Not everyone agrees on the details. Another theory points to the anterior cerebral artery, a blood vessel that supplies part of the front of the brain. In this view, cold triggers a rush of blood through that artery, and the extra pressure brings on the pain.
When the artery narrows again, the pain fades. Some suggest this quick widening and tightening may be a way the brain protects itself.
Part of the reason the debate continues is that brain freeze is surprisingly hard to study. It's over so quickly that researchers have said it's difficult to examine, and not much research has been done on it.
Speed Makes a Difference
The research that does exist has a clear lesson: slow down. In one study, 27 percent of people who ate an ice cream sample in under five seconds got a headache, compared with 12 percent of those who took longer than thirty seconds.
One study also found that children were more likely to get brain freeze than adults, which may mean people become less sensitive as they grow up. And contrary to popular belief, it can happen in hot weather or cold, because what matters is the temperature of the food, not the air.
Brain freeze usually lasts from a few seconds to a few minutes. If you have headaches that worry you, talk to your doctor.
A Headache With a History
People have been wincing over cold treats for centuries. According to The New Yorker, the first written account comes from Patrick Brydone in the 1770s. He described a British naval officer in Sicily who took a large bite of ice cream and spat it out “with a horrid oath.”
The term ice-cream headache was in use by 1937. Brain freeze first appeared in print in that sense in 1986, and 7-Eleven has registered the term as a trademark.
So the next time a milkshake ambushes you, take comfort: your brain isn't actually freezing. It's just getting a slightly garbled message from the roof of your mouth. Take smaller sips, and enjoy the rest of it.
