I really enjoy ice cream,

ice tea,

and sometimes just plain ice.

What I don't enjoy? Ice cream headaches.

Also known as brain freeze.

Why exactly does eating or drinking something

quickly create a sharp pain in the forehead?

After countless hours of exhaustive research,

I realized I could just Google my question.

Just kidding.

Here at Scientific American, we rely on primary sources

such as peer-reviewed research papers.

As it turns out, scientists have learned a lot about how brain freeze works

even though some of the details remain a mystery.

Blood vessels lining the roof of the mouth constrict

when exposed to something as cold as ice cream or a milkshake.

A few seconds later, they expand to their usual size.

According to one theory, this rapid constriction and expansion

triggers pain receptors on the roof of the mouth.

These receptors communicate with the brain via the trigeminal nerve,

a facial nerve whose branches spider across our nose, chin, cheek and forehead

which might explain why the brain perceives pain up here.

Another theory argues that the brain has a built-in defense mechanism

against sudden drops in temperature.

It keeps itself warm by increasing blood flow

through the interior cerebral artery just behind the eyes.

A recent study examined blood flow inside people's heads

as they sipped ice water through a straw.

(Sound of sipping) Ouch!

When the interior cerebral artery expanded,

they felt that familiar sharp pain in their forehead

But when the artery relaxed, the pain vanished.

Brain freeze usually disappears after a few seconds

and rarely lasts longer than a minute or two.

But there are ways to get rid of it and to avoid it altogether.

Pressing your tongue to the roof of your mouth

may help warm blood vessels more quickly

shortening the duration of your ice cream headache.

Eating or drinking cold things

slowly helps prevent brain freeze in the first place.

And if you're a fan of the extreme,

you can always eat your frozen treats in the freezing cold.

It's much more difficult to experience brain freeze

if your body is already battling low temperatures.

For Scientific American's Instant Egghead, I'm Ferris Jabr.