Originally scientists believed that brain freezes were caused by rapid cooling and rewarming of blood vessels in the sinuses, however, a recent study conducted in part by Harvard Medical School revealed that the true cause is a self-defense mechanism for the brain. During the study, participants were given ice-water and subjected to Doppler imaging to study blood flow in the brain during an ice cream headache. They found a rapid dilation of the anterior cerebral artery, which floods the brain with blood and causes pain until the vessel constricts.
“The brain is one of the relatively important organs in the body, and it needs to be working all the time,… It’s fairly sensitive to temperature, so vasodilation might be moving warm blood inside tissue to make sure the brain stays warm.”
Researchers also found that, due to the skull’s rigidity, an increase in blood volume in the brain causes an increase in pressure, which induces pain. They believe similar blood flow alterations could induce migraines and other types of headaches, meaning the research could lead to the development of new drugs that can affect dilation of blood vessels and give sufferers some much needed relief.