A quick-onset headache
If the pain in your head occurred suddenly and is unbearably bad, you could have a brain aneurysm, a bulge in the wall of an artery. Left untreated, the blood vessel could burst, leading to a potentially fatal stroke or massive brain bleed. Call the ambulance immediately.
Tooth pain when you drink something cold
If the enamel (the outside layer of your tooth) is damaged or decaying, it can expose the nerve inside your tooth, leaving you with intolerable pain when the area comes into contact with any cold or hot substances. In addition to the sensitivity, an exposed nerve also puts you at risk for a bacterial infection that can spread to other parts of your body. See your dentist if you start experiencing extreme tooth sensitivity.