Dr. Oz explains brain freeze.

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Question 15: What causes "brain freeze"?
A) Dehydration
B) Immune system
C) Cold temperature and lactic acid
D) Dilation of arteries

The correct answer is D.

If you are among the 30 percent of people who get headaches when they eat ice cream too fast, Dr. Oz says the dilation of your arteries is to blame. "When you eat ice cream, it actually stimulates the back of your mouth because it's cold and the arteries spasm," he says. "But after they close down, they relax, and that lets too much blood go to your brain, and you get the headache."

How do you get rid of the painful ache? Dr. Oz says you should hold your tongue at the top of your mouth to warm it up between bites of ice cream.