Harvard Women's Health Watch

By the way, doctor: What causes ice-cream headache?

Q. What exactly happens when I eat something cold and get an ice-cream headache? Is it harmful in any way?

A. Ice-cream headache, also known as "brain freeze" or cold-stimulus headache, is a headache some people get when they consume a cold food or beverage quickly. The pain is usually in the forehead or both temples, and it usually lasts less than five minutes.

The cause is debated, but most experts believe it starts when a cold substance touches the roof of the mouth or the back of the throat and causes small blood vessels in those areas to constrict and then rapidly dilate. Pain receptors near the blood vessels sense the discomfort and send the message along tiny nerve fibers to a larger nerve (the trigeminal nerve), which forwards it to the brain. The trigeminal nerve also carries pain signals from the face. The brain reads the cold-stimulus sensations as coming from the head rather than the mouth — a phenomenon called referred pain.

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