Here's a refreshing dilemma: why does something so delicious as ice-cream and slush puppies end up being so painful?

There’s a price to pay for overindulging, and rapidly consuming cold substances on a warm, sunny day, or even on a cold one.

Ice-cream headache, officially known as “headache attributed to ingestion or inhalation of cold stimulus”, is a brief pain, usually in the forehead and both temples, triggered by cold food, beverages, and sometimes even by breathing cold air. What exactly causes it is still an enigma, but one popular theory is that when cold stuff comes in contact with the roof of the mouth or the back of throat, it triggers the local blood vessels to enlarge (dilatation) briefly, followed by them getting narrower (constriction). The irritation of the blood vessel is sensed by local nerve endings, which send the message to the next big nerve they are connected to, the trigeminal nerve. In turn, the trigeminal nerve passes the signal on to the big boss, the brain. The brain interprets this signal as danger!, and thus sends back a pain message to tell the body to get away from it.

But wait a minute, if I am putting a “dangerous” gelato in my mouth, not rubbing it on my face, then why does my head hurt?! The middle man, the trigeminal nerve, is usually in charge of sensation in the face, so when the brain receives a signal from it, it thinks that the signal is coming from the face. This would explain why, when ingesting something cold, you feel pain in your forehead and temples, although the ice-cream was never near them. This common  phenomenon of perceiving pain in a location that differs from its origin is known as referred pain. A common example is that of pain during a heart attack: although it is the heart that is actually suffering, pain is often experienced both in the chest and in the arm. 

Another popular theory is that the change in temperature in the mouth is sensed by the carotid artery, running along the back of your throat, which signals one of the next big blood vessels and main brain arteries, the anterior cerebral artery, to dilate and thus send more warm blood to the brain in order to prevent it from freezing. Since the brain is locked in a bony cage, the skull, it has little space to accommodate the widened blood vessel, which leads to an increase in pressure inside the skull and thus a headache. However, the head senses the warm air around it, and thus quickly dismisses the original freezing danger signal as non-sense and tells the cerebral artery to take a chill pill. This would explain why ice-cream headache lasts for less than 5 minutes (often even less than 30 seconds).

Fun fact: the pain you feel is irritation of the coverings of the brain, the meninges, not the brain itself (the brain does not have pain receptors).

This post was written by Sandra Nagy, who studied medicine and is currently pursuing her PhD in the direction of gynaecology.