Clinical picture, risk factors and classification
Hand eczema can be classified on the basis of aetiology, morphology and/or localisation (1). It is also useful clinically to distinguish between acute and chronic eczema (1).
Acute hand eczema usually presents as erythema, oedema, vesicles and papules. The rash usually begins as pruritic millimetre-sized vesicles, often located on the palms and on the sides of the fingers.
Chronic hand eczema is characterised by erythema, oedema, skin thickening, scaling, fissures and erosions. Cases typically have a duration of more than three months, with three or more flares in the previous year, in the absence of any other underlying disease or infection and with no response to local steroid therapy (6).
Endogenous risk factors include changes in the skin barrier such as atopic eczema (7, 8). Mutation of the gene for filaggrin, a barrier protein in the skin, is a risk factor for both atopic eczema and chronic hand eczema (9).
Exogenous risk factors can be divided into two main groups: irritant and allergic hand eczema.
Irritant hand eczema is the result of an inflammatory reaction following exposure to chemical, physical and/or mechanical irritants. The commonest cause is wet work Box 1) ((10). Occupational groups that are particularly exposed to wet work include hairdressers, healthcare personnel, cleaners, kitchen/canteen workers, mechanics, construction workers and farmers (4, 11). Women and young workers tend to be most exposed (3, 4). Irritant hand eczema is a diagnosis of exclusion, and patients must be assessed for possible allergy-related causes of the eczema (2).
Box 1 Definition of wet work (10)
Wet work is work in which the hands:
are in contact with water for two hours or more per day,
are washed more than 20 times per day, or
are covered by tight gloves for two hours or more per day
Allergic hand eczema occurs as a result of skin contact with a substance that triggers an immunological response, most often a cell-mediated immunological response (type IV). Frequent occupational allergens are hair dyes, preservatives, metals, rubber, formaldehyde, epoxy, acrylates and isocyanates (11). The most vulnerable occupational groups include hairdressers, mechanics, welders and dentists (11) (Figure 2).
Protein contact dermatitis is a subtype of allergic contact eczema. It is triggered by skin contact with a protein that initiates an IgE-mediated immunological response (type I) with subsequent development of eczema. The exact pathophysiological mechanism is unknown. The patient will report stinging, itching and burning seconds to minutes after exposure to the relevant protein. Protein contact dermatitis occurs in occupations involving wet work and frequent skin contact with proteins from food, animals and/or plants. Vulnerable occupational groups include chefs, fishermen, bakers, veterinarians and veterinary nurses (11).