Question: why do people get brain freeze

Keith Siew answered on 25 Jun 2013:

Dear msimpson,

Now your questions has to be one of my favourites… because I have been thinking about it for some time to work out why we do get brain freeze and I had to go off and talk with some neuroscience friends and double check with a few google searches and wiki articles!

So… there is a bit of controversy out there over the cause and reason behind brain freeze… but it seems to boil down to this…

When something cold touches a part of your body the natural response is for blood vessels to constrict to move blood away from that part of the body to the “core”… this way it prevents heat loss and conserves the “core body temperature”… okay so we’ll bear that bit in mind first. The body in response to heat does the opposite and cause blood vessel dilations to move blood near the skin surface to lose excess heat!

Second… Our bodies can’t measure absolute temperatures but only relative differences… so for example… if you’re out playing in the snow… or a really cold wet windy day and you get into your home and put a cold foot in a warm bath… or shivering hands under the hot tap… it feels like the water is practically on fire and burning your skin… well it’s not… but your body thinks the temperature difference is so great that it must be causing some sort of damage to you… burning you! That coupled with the rapid change from constricted to dilated vessels causes a rapid return of blood to the skin which can cause a bit of a shock to the system… sort of the whole “pins and needles” idea… if a part of the body has had reduced blood supply the sudden return can have some “unusual effects”… one of them being discomfort and sometimes pain.

So let’s get back to the brain freeze now that we know about these two things… blood vessels and temperature sensation…

If you eat some lovely cold ice-cream… really fast… well that will touch the palate (roof of your mouth) and as it goes down your oesophagus (the food tube) it will also touch this! That rapid change from the bodies normal 37C to coming into contact with something 0C and below cause the blood vessels to constrict but because you swallow the ice-cream and your body internally is warm the blood vessels will dilate again rapidly causing a return of blood… so that rapid change is probably the first step… then the extreme change in temperature probably is perceived as dangerous by the body and so is experienced as “pain” there or at least discomfort… but because a major nerve that supplies the face goes through there… you get what is called “referred pain”… so even though you don’t have any pain being experienced in your forehead where you’re likely feeling the intense “brain freeze”, the fact that the same nerve further down the in the roof of your mouth has been stimulated the brain is fooled into thinking this is where the pain is… (You could do the same thing by sticking needles into the spinal cord to cause sensations in different parts of the body without actually touching them!)

So in a nutshell the rapid changes in temperature that the body sense and reacts to… stimulate a nerve that supplies the face and causes brain freeze… but in actual fact… there is no real danger or harm being cause… just a brief unpleasant experience… telling you to slow down and eat it slower!