THE ULTIMATE ICE CREAM QUESTION:

What causes an ice cream headache??

Short-lived headaches may occur after eating very cold foods or foods high in nitrites or monosodium glutamate. Headache pain does not involve the brain tissue or bones of the skull, which are insensitive to pain. Headache pain is associated with nerves and blood vessels around the brain; certain nerves of the face, mouth, and throat; and the muscles in the head and neck. When the nerves in these structures become over-stimulated, inflamed, or damaged, pain signals flash along neural pathways to the brain, and the person experiences a headache.
(Compton's Interactive Encyclopedia)