If you've never had a brain freeze, you're lucky. Most of us get a headache when we eat ice cream or something else really cold.

So what causes the dreaded ice cream headache? I asked my friend Dr. John Swartzberg at the UC Berkeley Wellness Letter.

"When it's really cold on the top or the roof of your mouth, it stimulates one of the cranial nerves, one of the nerves that goes to your brain and causes horrific pain that most of us have experienced," he said.

And how do you avoid this?

"Eat ice cold foods really slowly and if it happens to counter it put some warm water or lukewarm in your mouth or just press the tongue, your tongue to the roof of your mouth."

While we're talking about your body and the strange things it does, let's turn to goose bumps.

"It's what's called a vestigial response, sort of a reflex that we no longer need," Swartzberg said. "It was when our ancestors had lots of body hair and when they were frightened they could make them look larger by having the hair stand on edge."

It's what a cat does when it feels threatened. Humans no longer have to do that.

By the way, they're called goose bumps because they look like the skin of a goose after the feathers have been plucked.