Mammalian skin often contains hairs, Skin Care which in sufficient density is called fur. The hair mainly serves to augment the insulation the skin provides, but can also serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is very hard and thick, and can be processed to compose leather. Amphibian skin is not a strong barrier to passage of chemicals and is often subject to osmosis. A frog sitting in an anesthetic solution could quickly go to sleep.

Protection: an anatomical barrier from pathogens and affliction between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.