A cross-section diagram of a layer of skin is shown wherein the skin is represented by a thick brown layer and 3 pores are represented by ducts which are passing through the skin. As the Body heat increases, the skin reddens and the pores widen. Sweat then comes up to the surface of the skin through the widened pores and collects on the skin surface. Water molecules included in the sweat is represented by space-filling models. At the surface of the skin, the water molecules are connected to the adjacent water molecules through hydrogen bonds represented by dotted lines. Eventually, the pores width decreases. As the transfer of heat from skin to sweat takes place, the skin color normalizes, the water molecules vibrate intensely and the hydrogen bonds between the water molecules break up. Later, the sweat at the surface of the skin evaporates completely.
Sweating cools you off because the fastest-moving (hottest) water molecules break every hydrogen bond and escape, carrying away heat. The escape is evaporation, so this way of losing heat is called evaporative cooling. Plants and many animals cool themselves in this way. It can be dangerous if too much water is lost, but it's worth the risk if the alternative is fatal overheating.