Why eating cold food too fast causes brain freeze

HostWe have all been there on a hot day. You grab a cold milk shake or a big scoop of ice cream, take a huge bite, and then it hits you. A sharp, stabbing pain right behind your eyes that makes you want to hold your head and wait for the world to stop spinning. We call it brain freeze, and while it only lasts a minute, it feels like forever.

HostWhy does our body react so violently to something as simple as a cold treat?

GuestIt's a bit of a shock to the system, isn't it? The first thing to know is that your brain isn't actually freezing. If it were, you would've much bigger problems than a quick headache. What's really happening is a big mix-up in how your body handles a sudden change in heat. It all starts at the roof of your mouth. Right there, behind your top teeth, you have a lot of very sensitive blood vessels and a big knot of nerves. When you swallow something icy too fast, you're basically throwing a bucket of ice water on a very delicate part of your internal plumbing.

HostBut my mouth is the part that's cold. Why does the pain show up in my forehead? It feels like the ice cream is actually inside my skull, but I know it's just in my throat.

GuestThat's the weirdest part of the whole thing. It's called referred pain. Your body isn't always great at telling exactly where a signal is coming from. There's a major nerve that handles feelings for your face, your jaw, and the roof of your mouth. When those cold sensors in your mouth start screaming, the signal travels up to your brain. But because that same nerve also covers your forehead and your eyes, your brain gets confused. It thinks the pain is coming from your forehead instead of your mouth. It's kind of like a crossed wire in a house. You flip a switch in the kitchen, but the light in the hallway turns on instead.

HostOkay, I get the confusion part, but why does it have to hurt so much? If the mouth gets cold, shouldn't the body just warm it up? Why the stabbing feeling?

GuestWell, the pain comes from the way your blood vessels react. When that cold hits, the vessels in the roof of your mouth tighten up fast to try and keep heat in. But then, almost immediately, your brain sends a massive burst of blood to that area to warm it back up. It's like a floodgate opening. Those vessels widen way too fast, and that sudden change in size and pressure sets off the pain sensors. Your brain is a bit of a heat hog. It needs to stay at a very steady temperature to work right. When it senses a sudden chill nearby, it panics and tries to fix it by pumping in as much warm blood as possible.

HostWait, if the brain wants to stay warm, that sounds like a good thing. I would think opening the blood vessels would feel good, like a warm blanket. It still doesn't explain why it feels like a knife.

GuestYou would think so, but the skull is a very tight space. There's not a lot of room for things to expand. When those vessels in your head suddenly swell up to bring in the heat, they push against the tissues around them. That quick stretching and pressure is what your nerves pick up as pain. It's actually a protective move. Your brain is trying to warn you to stop doing whatever is making it cold. It's a very loud, very painful alarm bell that says, hey, slow down, you're chilling the most important organ in the body.

HostSo it's just a big overreaction. My brain thinks it's in danger of freezing solid just because I took a big bite of a slushie. It seems like a pretty clumsy way for such a smart organ to handle a snack.

GuestIt's a bit dramatic, yeah. But you have to remember that for most of human history, we weren't eating ice cream at sub-zero temperatures. Our bodies are built to survive in the wild, where a sudden drop in head temperature usually means something is very wrong. We're basically using an ancient survival tool to handle a modern dessert. And some people get it way worse than others. About a third of people seem to be prone to this, while others can eat a whole pint of ice cream without a single twitch. We're not entirely sure why, but it might just be that some people have more sensitive nerves or blood vessels that react more jumpily to the cold.

HostIs there any way to make it stop once the alarm starts going off? I usually just press my hand against my head and hope for the best.

GuestThere's actually a better trick. Since the whole problem started because the roof of your mouth got too cold, you need to warm that specific spot back up. The fastest way to do that's to press your tongue against the roof of your mouth. Your tongue is full of warm blood, so it works like a little heating pad. You can also try drinking something room temperature. You're basically trying to tell those nerves and blood vessels that the frostbite scare is over and they can relax.

HostThe next time I grab a cold drink, I'll try to remember that my tongue is the secret weapon against that forehead sting.

GuestJust remember that your brain is only trying to look out for itself by sounding that very loud, very chilly alarm.

HostThat milk shake might be delicious, but a warm tongue on the roof of the mouth is the only thing that will keep the brain from sounding the sirens.