Do you really lose most of your body heat through your head?

No. The idea that the head accounts for most of the body's heat loss, sometimes put as high as 80 percent, is a myth. Sources from NOAA, WebMD, Healthline and the University of Rochester all say the body loses heat in proportion to how much of it is exposed. The head is a small part of the body's surface, so it cannot account for most of the loss. [1] [2] [3] [4]

Estimates of the head's share of body surface vary slightly. NOAA puts it at about 7 percent, and says it loses heat at about the same rate as any other 7 percent of exposed body. WebMD and Healthline give 10 percent and 7 to 10 percent respectively. Richard Ingebretsen, a wilderness medicine expert at the University of Utah, notes that if the head lost 75 percent of the body's heat from about 10 percent of the area, it would have to lose roughly 40 times as much heat per unit area as the rest of the body. He describes that as unlikely and says tests on college students found the same heat loss whatever area was exposed. [1] [2] [3]

Nigel Taylor, a thermal physiologist at the University of Wollongong, writes that the head is not an ideal radiator despite its many surface blood vessels. Its skin blood flow barely changes whether a person is comfortable or greatly cooled, and even in dangerous overheating it rises much less than in the hands and feet. About half of a typical head is covered in insulating hair. In his account, the head's share of evaporative cooling at rest is only about 10 percent, rising to 13 percent during exercise. His conclusion is that covering the head is no more effective than covering most other body regions, with the hands and feet the exceptions where heat loss is greater. [5]

BBC Science Focus says the myth likely stems from a US Army Field Manual that stated 40 to 45 percent of heat loss occurs through the head. It also notes that the face, head and chest are more sensitive to temperature changes, so covering them feels as though it prevents more heat loss. Ingebretsen offers a further explanation: in the cold we are usually clothed everywhere except the head, so a bare head is where the heat escapes. Without a hat, you lose heat through your head just as you would through bare legs in shorts. [6] [2]

The University of Rochester notes that wearing a hat is still a good idea, but other exposed parts need covering too. The amount of heat lost through the head depends on factors such as hair thickness and how much energy a person is using in the cold. A child's head is a larger proportion of body surface than an adult's, so children lose proportionally more heat through it, and hoods and hats matter more for them. [4]