The epidermis is the outer layer of the skin and contains no blood vessels or nerve endings. The cells on the surface are gradually shed and replaced by new cells that have developed from the deeper layers; this process takes approximately 28 days. The epidermis has hairs, sweat glands and the ducts of sebaceous glands passing through it. It provides a protective barrier for the internal organs (Farage et al. [61]) and an efficient natural barrier against the potential threats posed by the external environment, such as pathogens and physical trauma (Jones [97], Marks and Miller [118], Maurer et al. [123]).

The dermis is the thickest layer of skin and contains blood and lymph vessels, nerve fibres, sweat and sebaceous glands. It is made up of white fibrous tissue and yellow elastic fibres, which give the skin its toughness and elasticity. It provides the epidermis with structural and nutritional support (Jones [97]).

The subcutaneous layer contains the deep fat cells (areolar and adipose tissue) and provides heat regulation for the body. It is also the support structure for the outer layers of the skin. Maintaining skin integrity, through good personal hygiene, will allow this complex system to provide an efficient natural barrier against the external environment.

It is important to remember that the skin is an adaptive organ, affected by internal and external factors such as temperature, air humidity and age (Slominski et al. [214]). It has great ability to adapt to changes in the environment and stimuli but is affected by ill health, immobility and malnutrition (Dunk [54], Leaker [105]). Its integrity, continuity and cleanliness are essential to maintaining its physiological functions.

The ageing process can adversely affect the skin's structure (Farage et al. [61]). Skin tissue becomes thinner, less elastic and less resistant to trauma and shearing forces. The blood supply is reduced as cells are replaced more slowly, which can adversely affect healing. Transmission of stimuli from sensory receptors slows, so reaction to warning stimuli produced by the sensory receptors can be delayed and result in damage. The production of natural oils declines and can lead to dry skin, which increases the risk of infection and tissue breakdown (Kottner et al. [101]). Nursing interventions for skin care can protect, maintain and promote skin integrity (Cowdell and Steventon [42], Farage et al. [61]).