Believe it or not, this has been the topic of research in the past and even has a medical diagnosis called "sphenopalatine ganglioneuralgia". To sum it up, there are two theories behind this phenomenon: 1) Blood vessel phenomenon: Blood vessels constrict when any part of the body is exposed to cold temperature and dilates when it gets hot. This simple fact can be applied to the biological cause of brain freeze as well. Upon contact with ice, the blood vessels in the roof of the mo…