A cold-stimulus headache, colloquially known as an ice-cream headache or brain freeze, is a form of brief pain or headache commonly associated with consumption (particularly quick consumption) of cold beverages or foods such as ice cream, popsicles, and snow cones. It is caused by a cold substance touching the roof of the mouth, and is believed to result from a nerve response causing rapid constriction and swelling of blood vessels, "referring" pain from the roof of the mouth to the head. The rate of intake for cold foods has been studied as a contributing factor. It can also occur during a sudden exposure of unprotected head to cold temperatures, such as by diving into cold water. A cold-stimulus headache is distinct from dentin hypersensitivity, a type of dental pain that can occur under similar circumstances.
Cats and other animals have been observed exhibiting a similar reaction when presented with a similar stimulus.
Terminology
The term ice-cream headache has been in use since at least January 31, 1937, contained in a journal entry by Rebecca Timbres published in the 1939 book We Didn't Ask...