Diseases of the skin
Non-infective dermatitis
The term 'dermatitis' simply means an inflammation of the skin. When the condition is due to contact with a substance at work it is called 'occupational' or ' industrial' dermatitis. It is a common cause of occupational disease but the number of cases is declining owing to improved work conditions.
The skin has two layers; the outer layer called the 'epidermis' and the inner 'dermis'. The epidermis has a protective function. It consists of densely packed flat cells, thicker in some areas, like the palms of the hands, which are more subject to injury. It is covered by a moist film known as an 'acid mantle', made up of secretions from sweat and sebaceous glands, that helps to protect from acids, alkalis and also excessive water, and to some degree from heat and friction by preventing the skin from drying out. The natural grease of the skin can be removed by solvents, in the deeper layer of the epidermis are pigment cells which produce the 'tan' following exposure to sunlight and protest the body from ultraviolet radiation.
Some persons are more susceptible to skin damage than others, particularly the young, those with soft, sweaty skin, the fair complexioned and those with poor personal hygiene. Occupational dermatitis can affect any part of the body, but the hands, wrists and forearms are most commonly involved. Damage to the skin may follow exposure to chemical and biological substances and well as physical agents. Dermatitis is of two kinds: irritative and sensitising - the former is four times more common. Chemicals which cause irritative dermatitis include acids, cement solvents, some metals and their salts. The effect on the skin depends ion the concentration and duration of exposure, and will affect most people in contact with them. At first the response may be minor, but it worsens with repeated contact.
Sensitisers, on the other hand, do not cause dermatitis until the individual has first become sensitised to them. This involves an allergic response in the blood initially, the dermatitis following on subsequent exposure. Once sensitisation has occurred a small dose may be sufficient to cause a rash. Sensitisers include chrome-salts, nickel, cobalt, plastics made of epoxy, formaldehyde, urea or phenolic resins, rubber additives, some woods and plants. Some substances act as both irritant and sensitiser, e.g. chrome, nickel, turpentine and mercury compounds.
Symptoms
The onset of dermatitis may be unnoticed, especially as it usually clears up when away from work, i.e. at weekends and holidays. On return to work and further exposure the condition recurs, worsening with each subsequent contact. The skin, at first rough and raw, may itch, become cracked and sore, prompting the individual to see medical advice. The rash may be diffuse, as with eczema, or pimple like as with acne - the former following exposure to irritative and sensitising agents, and the latter from exposure to mineral oils, pitch, chlorinated hydrocarbons. Patch testing, in which a dilute quantity of chemical is applied to the skin under a plaster and left for several hours to see if a reaction develops, is useful only for determining allergic response to chemicals but requires specialist interpretation.
Protective measures
Persons with dermatitis or sensitive skin may need to be excluded from certain kinds of work. Good personal hygiene is essential and barrier creams may be helpful. Protect clothing should be considered.
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