Eating ice cream rapidly can induce a "brain freeze" or sphenopalatine ganglioneuralgia. When cold substances come into contact with the roof of the mouth, blood vessels constrict and then rapidly dilate, triggering pain signals to the brain. Additionally, consuming ice cream quickly may lead to a sudden drop in temperature in the stomach, prompting the body to redirect blood flow to maintain core warmth. This shift in blood flow can affect the blood vessels in the head, potentially contributing to a headache.