The recognition of skin disorders is essentially a visual art. It requires experience to distinguish what is dermatitis or eczema from what is not; disorders that might be confused with dermatitis or eczema include such conditions as diffuse skin malignancies, known as reticuloses, or infections either fungal or parasitic.

Dermatitis which develops in response to contact with a foreign, but not necessarily a newly-contacted, substance is called Contact Dermatitis. There are two broad types: the irritant, and the allergic.

The recognition of allergic contact dermatitis is more important than that of any other dermatitis, for it is the only one which can be cured by appropriate treatment, namely removal of the offending allergens.

The development of allergic contact dermatitis depends upon the patient being specifically allergic to the allergen which becomes bound to skin cells. In the epidermis, wandering cells identify the allergen as foreign, pick up one of its molecules and take it to the nearest lymph node, where it is clearly identified as an enemy; consequently millions of white blood cells, lymphocytes, are sent on the war path to identify and destroy other similar molecules. Their method of destruction may be one of many. The cell may release powerful harmful substances that destroy not only the molecules, but also many innocent surrounding cells and tissues. This process results in blister formation, and even sloughing off of the outer skin layers.

Swelling and redness may result, along with increased blood flow; more and different kinds of warrior cells and other cells, called macrophages, that pick up or phagocytose foreign and dead matter, may arrive on the scene. More harmful chemicals are then released and the process appears to have become ‘inflamed’, and then to have ‘cured* the trouble; subsequently, things return to normal. Once the skin is sensitized, each contact with the same or closely related contact allergen (or enemy f will produce an identical response. Some of the commoner allergies will be discussed in turn.

Nickel is the commonest sensitizer in women, and its main sources are jewellery, watches, stainless steel, clothing fasteners and the famous but now uncommon suspender belt. The areas usually involved are the back of the neck, ear lobes, wrist, fingers, and underneath nickel-containing fasteners, (for example, underneath bra straps). Nickel sensitivity is common in hand eczema, affecting the sides of the fingers (caused by contact with such things as scissors and knitting needles).

Chromium is the commonest sensitizer in men. and is the commonest cause of occupational allergic contact dermatitis. Chromium is very widely distributed, being found in cement, stainless steel, chromium plating, anti-dust paint, cutting oils, printing plate cleaners, leather and dyes. It causes eczema on the hands, arms and face.

Rubber Pure rubber is non-allergenic, but antioxidants, accelerators and vukanizers used in the process of stabilizing

the liquid latex may sensitize the skin. Allergic contact dermatitis is particularly associated with wearing rubber gloves, rubberized underwear and shoes, and with contact with such items as rubber bands and electric cables. Industrial rubber dermatitis is seen in tyre workers as a chronic hand eczema. It is caused by the vulcanizing agents related to p-phenylene diamine (PPD).

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