19 Skin performs multiple functions:
Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense.
Sensation: contains a variety of nerve endings that react to heat, cold, touch, pressure, vibration, and tissue injury.
Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation,
convection and conduction. Dilated blood vessels increase perfusion and heat loss while constricted vessels greatly reduce cutaneous blood
flow and conserve heat. Control of evaporation: the skin provides a relatively dry and
impermeable barrier to fluid loss. Loss of this function contributes to the massive fluid loss in burns.
Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D.
Excretion: sweat contains urea, however its concentration is 1130th that of urine, hence excretion by sweating is at most a secondary
function to temperature regulation. Absorption: While skin acts as a barrier some chemicals are readily
absorbed through it. Water resistance: The skin acts as a water resistant barrier so essential
nutrients arent washed out of the body. The skin can be affected by chemical, physical and biological agents and skin
disorders account for a substantial proportion of industrial diseases. The types of effect can be classified into; dermatitis, physical damage, cancer, biological
and other effects.
2.1.1 Dermatitis
The most common disorder is contact dermatitis and 70 of cases are due to primary irritation i.e. direct action on the skin, most often of the hands and
forearms. An irritant is an agent that directly damages cells if applied to the skin in sufficient concentration and for sufficient time i.e. all effects are dose-
related, leading to irritant contact dermatitis. Alkalis dissolve keratin and
20 some solvents remove the sebum. Any direct skin effects can make the
surface more vulnerable to other agents and reduce the skins entry defences. The other form of contact dermatitis is allergic contact dermatitis. This results
from sensitising the skin by initial contact with a substance and subsequent re-contact. A sensitizer allergen is a substance that can induce a specific
immunological sensitivity to itself. The initial dose may need to be quite high and leads to a delayed-type hypersensitivity response mediated by
lymphocytes and involving antibody production. The first dose produces no visible effects but subsequent, often minute, exposures may lead to
dermatitis. Common irritants include detergents, soaps, organic solvents, acids and
alkalis. Common
sensitizers are
plants gardening,
antibiotics pharmaceutical industry, dyes paint and cosmetic industry, metals nickel
usually non-industrial, and chromates cement industry, rubbers and resins.
People working with cutting oils can have both irritant and allergic contact dermatitis, being irritated by the oil itself and allergic to biocides within it.
2.1.2 Physical damage
Physical agents which can harm the skin include weather, friction and injury. Cold, wind and rain cause dry chapped skin, and sunlight can burn or cause
skin tumours, so occupations exposed to the elements fishing, farming are at risk. Friction injuries are common in heavy manual labouring construction and
mining, and sharp equipment used in many occupations can lead to abrasions and lacerations.
2.1.3 Biological agents
