Why do doctors put the thermometer under your tongue when checking for a fever?
That's just one of the spots a fever is most evident
There are a few spots that can accurately display your internal temperature on your body. Under the tongue is one of those spots.
It is a lot better than the other possible place they use to get an accurate reading. If you read the box when you buy a rectal thermometer, it says "Each thermometer is individually tested" I wonder how they do that!