The short answer

A brain freeze is caused your body's response to the rapid cooling of the blood vessels in the roof of the mouth.

The long answer

A brain freeze is caused by eating or drinking something cold too quickly – we all know that.

But what's actually happening inside our bodies when we experience brain freeze? When our bodies come into contact with cold temperatures, the blood vessels in the exposed area automatically constrict to reduce the amount of heat lost on the surface.

During the sudden drop in temperature caused by a brain freeze, the trigeminal nerve (responsible for the sensations in the face) triggers the blood vessels in your mouth to narrow. But to adjust for the rapid temperature change, your brain also very quickly sends a rush of blood to the roof of your mouth to warm up the area, causing the blood vessels to swell.

The rapid fluctuation in blood vessel size is what causes a pain sensation. But because your body is able to bring the roof of your mouth back to a normal temperature quickly, the pain goes away in seconds or minutes.

If you can't bear the pain of a brain freeze, you can try to warm the area by pressing your tongue to the roof of your mouth or drinking warm water.

🧠 Bonus brain points

People who experience migraines are more likely to experience brain freezes. We don't know why exactly, but the theory is that some people's trigeminal nerves are more sensitive than others.

Sources

Cleveland Clinic. (2021, February 2). Brain Freeze. Cleveland Clinic. Retrieved April 12, 2023, from https://my.clevelandclinic.org/health/diseases/21478-brain-freeze

McCallum, K. (2020, July 9). What Causes Brain Freeze? Houston Methodist On Health. Retrieved April 12, 2023, from https://www.houstonmethodist.org/blog/articles/2020/jun/what-causes-brain-freeze/

Woehnker, K. (2020, August 21). What Causes Brain Freeze? Hackensack Meridian Health. Retrieved April 12, 2023, from https://www.hackensackmeridianhealth.org/en/healthu/2020/08/21/what-causes-brain-freeze