Body temperature tends to increase as a result of exercise, fever, or an increase in environmental temperature. Homeostasis is maintained by the loss of excess heat. The blood vessels (arterioles) in the dermis dilate and allow more blood to flow through the skin, thus transferring heat from deeper tissues to the skin. To counteract environmental heat gain or to get rid of excess heat produced by the body, sweat is produced. The sweat spreads over the surface of the skin, and as it evaporates, heat is lost from the body.

If body temperature drops below normal, heat can be conserved by a decrease in the diameter of dermal blood vessels, thus reducing blood flow to the skin. With less warm blood flowing through the skin, however, the skin temperature decreases. If the skin temperature drops below approximately 15 degrees Celsius, blood vessels constrict, which helps to prevent tissue damage from the cold.

Contraction of the arrector pili muscles causes hair to stand on end, but with the sparse amount of hair covering the body, this does not significantly reduce heat loss in humans. Hair on the head, however, is an effective insulator.