Talk about a buzz kill: You’re enjoying a delicious Slurpee or margarita when you get a piercing headache. This probably happens when capillaries in the roof of your mouth become dilated from coming into contact with an icy substance, says Mark W. Green, M.D., director of headache medicine at the Columbia University College of Dental Medicine. A message is then sent to your brain, and in response blood vessels can swell, resulting in a brain freeze. The cure? Simply press your tongue to the roof of your mouth to warm it, or drink a glass of warm water.