‘Always keep your head covered. You can lose 40–45% of body heat from an unprotected head.” That’s the advice in a 1970s US Army Survival Manual, which is probably where this myth originated, says John Tregoning, a professor of vaccine immunology at Imperial College London.
The reality is that there is nothing special about your head. When you go out in the cold, you lose more body heat from any area you leave exposed than from those parts protected by clothing. Out in a snowsuit but no hat? You’re going to lose heat quickly from your face and head, while the suit slows down the cooling of your body.
