This question actually came from my husband, but I have wondered this before myself, and been asked by others. What causes brain freeze, or ice-cream headaches?
There’s just nothing worse than brain freeze, is there? Well, okay, there are many things worse, but it’s particularly upsetting as it usually comes when you’re enjoying ice-cream, or an ice lolly, or a long cold refreshing drink on a hot day. Plus, I just find it fascinating how our bodies respond to the world around us, and how simple things can cause seemingly unrelated responses… because I’ve always found it bizarre that eating or drinking something cold can actually make your head hurt. It’s a strange sensation, as well, it doesn’t feel like anything else I’ve experienced, so I’ve always wondered what is going on.
It turns out, what’s happening is a really good demonstration of how your body responds to the outside world, and how your brain interprets messages. It’s pretty cool, actually. Pun 100% intended.
It’s clever, your body. It has awesome ways of regulating itself, including regulating its temperature. When something very cold hits the roof of your mouth, all the blood vessels just below the surface shrink and contract, probably shouting “yikes!” or other four letter words, in response to the sudden cold. I imagine messages being shouted all over the place… “it’s flipping freezing here, sort it out!”. Moments later, your body tries to sort it out by dilating all the blood vessels that have shrunk in the cold, forcing them to relax and widen out again. This increases blood flow to the area, which warms everything back up. So far, so good. Your blood vessels grumblingly get over the shock of having ice-cream applied to them without warning, and carry on carrying blood around.
However, that isn’t all that’s happening. The sudden dilation of the blood vessels triggers pain receptors. This is designed to let your brain know that something has suddenly changed, and all might not be well. Your pain receptors don’t understand that sometimes sudden cold can simply mean that you’re enjoying a refreshing ice-cold drink, because actually extreme cold can be dangerous, just like extreme heat, and so your pain receptors are programmed to interpret the sensation as potentially damaging, particularly when it’s very sudden or overwhelming, perhaps because you gulped down an iced drink, or tried to fit an entire Magnum in your mouth at once. This is the same reason that sometimes touching something incredibly cold can feel painful.
So, the pain receptors in your mouth aren’t aware that ice-cream is not a potentially harmful thing, they just notice that something might be wrong and they react in the standard way: they release chemicals, prostaglandins, whose job is to cause inflammation. This triggers a message to be sent to the brain along the trigeminal nerve that alerts the brain to the chilly danger. Your brain interprets the message as pain. The problem is that the trigeminal nerve doesn’t just carry messages from the mouth, though, it also receives and sends messages from the forehead and the sinuses. When the brain receives the “Hey! Cold stuff! Ouch!” messages, it doesn’t know precisely where they came from, and so it interprets the pain as coming from the wrong bit, which is why you feel the pain in your forehead, even though the cause is in your mouth. This is what is known as referred pain.
It usually takes about 10 seconds for your blood vessels to constrict, dilate, alarm your pain receptors enough that they alarm your brain, and for you to feel the referred pain. Luckily, however it doesn’t last long. And it is possible to try and avoid it, by not taking such large mouthfuls of ice-cream (I’m talking to myself here), and by generally putting very cold things in your mouth more slowly, and holding them there for longer, so your blood vessels can get accustomed and won’t panic quite so much.
And that’s it, the science behind brain freeze. I’m not sure this will necessarily be much comfort next time you have a face full of ice-cream and a headache, but I still think it’s pretty awesome to understand the way your body interprets the outside world and responds to it.