Through which mechanism does sweat primarily remove heat?

• A. Conduction from the skin.
• B. Evaporation from the skin.
• C. Radiation from the skin.
• D. Convection from the skin.

Answer: (B)

Sweat primarily removes heat through evaporation. When sweat sits on the skin and then evaporates, it absorbs a large amount of energy from the body to change from liquid water to water vapor. This latent heat of vaporization is substantial, so even small amounts of sweat can carry away a lot of heat and cool the skin and blood.

Conduction, convection, and radiation transfer heat between the body and the surroundings, but they don’t remove heat as efficiently as evaporation during sweating. Their effectiveness depends on contact with cooler surfaces, air movement, and temperature differences, whereas the cooling from sweat comes from the energy required to vaporize the water on the skin. If the environment is very humid or still, evaporation slows, reducing cooling, but evaporation remains the dominant mechanism when sweat is present.