Diseases of Hands-Skin Disorders

Allergic contact dermatitis, like atopic dermatitis, almost always begins on the dorsal surface of the fingers and hands. This predilection is most likely due to the protective effect of the thick keratin found on the palmar aspect of the fingers and hands. Allergic contact dermatitis differs from atopic dermatitis in that excoriations are less prominent and a visible eruption precedes the scratching. Before a diagnosis of allergic contact dermatitis can be proven, however, several things must occur: a suspected contactant must be identified; a positive result to patch testing must be obtained; and the patient must demonstrate improvement when the contaclant is removed. The most readily identifiable type of allergic contact dermatitis is that of nickel allergy because the emplion occurs in such close proximity to the offending ring, bracelet, or watchband. Many industrial chemicals cause allergic contact dermatitis of the hands. The agents most commonly involved are chromates and epoxy resins. Cosmetics (cinnamates, lanolin, Peruvian balsam) are occasional offenders. Soaps and detergents cause irritant, rather than allergic, contact dermatitis.

Irritant contact dermatitis is characterized by the presence of chapping, cracking, and fissuring. Inflammation, weeping, crusting, and excoriations are considerably less prominent. The changes of irritant contact dermatitis occur most commonly on the volar aspects of the fingers, but the palms and dorsal surface of the hands, particularly over the knuckles, may also be involved. The skin is dull red and often has a shiny or glistening surface. Tingling or burning pain is present; pruritus is not prominent. The diagnosis is based on the clinical appearance and on the history of frequent exposure to soap, water, or other solvents. Irritant contact dermatitis is an occupational hazard for mothers, housewives, waitresses, bartenders, and those in the health professions. A second type of irritant contact dermatitis occurs because of moisture retention and maceration under wide rings. Thus, eczematous changes around rings may be either allergic or irritant in etiology. Patch testing to metals may be necessary to differentiate between these two possibilities.

Scabies is an infrequent cause of hand eczema. It is characterized by initial development of solitary vesicles or inflammatory vesicopapules in the web spaces. From there, eczematous changes can spread onto the dorsal surface of the hands and fingers. The diagnosis is based on this distribution pattern, evidence of contagion, recovery of the mite, and the presence of typical lesions at other body sites.

Autoeczematization (or autosensitization) is a reaction pattern in which eczematous disease elsewhere on the skin induces "metastatic" eczematous lesions at some distant site. The hands, particularly the palms and fingers, are frequently involved in this reaction. A vesicular component that resembles dyshidrosis is often present. A diagnosis of autoeczematization is likely: (1 ) if vesiculation is explosive in onset, (2) if there is minimal grouping of the vesicles, and most importantly, (3) when marked eczematous disease is found on the feet or elsewhere on the body.

The diagnosis and therapy for hand eczema are complicated because more than a single process is frequently involved. Thus, dyshidrotic eczema, allergic contact dermatitis,

and scabies are often complicated by the concomitant presence of either the itch-scratch cycle (atopic dermatitis) or irritant contact dermatitis resulting from soap and water exposure. With so many processes occurring at once, it is easy to see why many clinicians give up trying to sort out the individual processes responsible for the problem and simply label it "hand eczema." Nevertheless, since the treatment varies with each of the processes, it is important to identify them individually. As mentioned above, where this cannot be done on the basis of history and examination, it may be necessary to use a short course of systemic steroids so that the initial characteristic changes can be identified as they recur.