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You take a big gulp of your milkshake, and you feel it—that ache shooting all the way up to the top of your head. What is that? Well, you know what it is, of course: it's a brain freeze. But just why do they happen in the first place?

Believe it or not, while brain freezes can happen to almost anyone, some people are actually more susceptible than others. Our bodies are pretty weird, and this reaction is all about how temperature, nerves, blood vessels, and pain pathways interact. Breathe out a sigh of relief, though: your brain itself isn’t actually freezing.

What Cold Does to Your Mouth and Nerves

First things first, what is a brain freeze, anyway? Also called an ice cream headache, this weird, temporary pain usually gets triggered when something very cold rapidly cools the roof of your mouth or the back of your throat. Anything you eat or drink, whether it's ice cream or a smoothie, can quickly induce this sensation. In fact, the faster the temperature changes, the more likely those sensitive tissues may be stimulated strongly enough to cause that throbbing pain.

But what are the nerves being affected? When there's a sudden temperature change, it activates certain sensory pathways, and chief among them is the trigeminal nerve. This major cranial nerve carries sensory information from much of the face and also plays an important role in several headache disorders. When cold receptors around the palate are stimulated abruptly, pain signals can travel through these pathways as well, thus causing the brain freeze you experience.

Here's another fun fact: the location of the pain is also an example of what doctors call referred pain—in other words, the cause of the injury is in a different spot than where you feel the pain. In brain freezes, though the trigger is in your mouth or throat, your nervous system interprets the incoming signals as pain in the head. The more you know!

Blood Vessels May Be Part of the Reaction

It's not just the trigeminal nerve at play, though; blood-vessel changes have long been proposed as another component of the brain-freeze response. One theory suggests that rapid cooling produces vascular changes as the body works to regulate temperature, which can in turn potentially activate pain-sensitive nerves. Scientists haven’t established one vascular pattern that explains every episode, however, so take it with a grain of salt.

Research on this hypothesis has produced interesting but somewhat varied results. For example, a 2019 study using transcranial sonography found increased blood flow in the middle cerebral arteries after participants drank ice water, suggesting the theory could be true. However, other studies have reported different vascular changes, which might mean there's more at play that we're still not completely sure of.

Whatever is happening behind the scenes, one thing's for sure: the reaction happens remarkably fast. Once the cold trigger is swallowed and the area starts warming again, the pain response usually settles down right away. Of course, everyone is different. Some people may never experience brain freezes at all.

Can You Prevent a Brain Freeze?

Okay, now that you kind of know what's going on, how do you prevent brain freezes from happening? The ache might be brief, but it can still be incredibly annoying to deal with, especially if you're prone to it. Well, one of the simplest ways to reduce your chances of getting brain freeze is to simply slow your pace when eating or drinking anything cold. Smaller bites and sips, after all, give the tissues inside your mouth more time to adjust instead of exposing them to a completely different temperature at once.

If you feel brain freeze starting, try warming the affected area. Stop eating or drinking the cold item and press your tongue against the roof of your mouth—this might help the tissue return toward its normal temperature faster. Similarly, you can switch to consuming something warm or at room temperature. These approaches won’t necessarily stop every episode, but they can still provide a bit of relief.

At the end of the day, brain freezes may be strange and (annoyingly) painful, but they're thankfully harmless. That means you don't need to give up your favorite ice cream or milkshake, but you should make sure to take it nice and slow when enjoying cold stuff. If you're especially prone, you can try different ways to warm your mouth, though you might still feel envious of those who don't experience brain freezes at all. Keep in mind, though: if headaches happen without a cold trigger, often last much longer, or feel unusually severe, they shouldn’t automatically be dismissed as ordinary brain freeze. Always make sure to chat with your doctor if anything feels off.