Functions of the skin for protecting the body from physical, chemical and biological threats. Inclusions: functions of protecting against the sun and other radiation, photosensitivity, pigmentation, quality of the skin, an insulating function of skin, callus formation, hardening; impairments such as broken skin, ulcers, bedsores and thinning of the skin.

Some rare conditions may involve blister formation, as in epidermolysis bullosa.