Mammalian skin often contains hairs, 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 ideal hard and thick, and can be processed to discover leather. Reptiles and fish have hard safeguarding scales on their skin for protection, and birds have hard feathers, all imaginary of healthy β-keratins. A frog sitting in Skin Care an anesthetic solution could quickly go to sleep.

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