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104 Clinical Dermatology TABLE 3-4 A llergic Hand Dermatitis: Some Possible Causes Allergens Sources Nickel Door knobs, handles on kitchen utensils, scissors, knitting nee dles, industrial equipment, hair dressing equipment Potassium dichromate Cement, leather articles (gloves), industrial machines, oils Rubber Gloves, industrial equipment (hoses, belts, cables) Fragrances Cosmetics, soaps, lubricants, topi cal medications Formaldehyde Wash-and-wear fabrics, paper, cos metics, embalming fluid Lanolin Topical lubricants and medications, cosmetics the source, is increased by further exposure to irritating chemicals, hand washing or scratching, medication, and infection. Inflammation of the dorsum of the hand is more often irritant or atopic than allergic. Treatment. Allergy may initially appear as acute, subacute, or chronic eczematous inflammation and is managed accordingly. FIGURE 3-23 Irritant hand dermatitis in a patient with atopic diathesis. Irritant eczema of the backs of the hands is a common form of adult atopic dermatitis. Allergic Contact Dermatitis Allergic contact dermatitis of the hands is not as common as irritant dermatitis. However, allergy as a possible cause of hand eczema, no matter what the pattern, should always be considered in the differential diagnosis; it may be investigated by patch testing in appropriate cases. The incidence of allergy in hand eczema was demonstrated by patch testing in a study of 220 patients with hand eczema. In 12% of the 220 patients, the diagnosis was established with the aid of a standard screening series now available in a modified form (T.R.U.E. Test). Another 5% of the cases were diagnosed as a result of testing with additional allergens. The hand eczema in these two groups (17%) changed dramatically after identification and avoidance of the allergens found by patch testing. Table 3-4 lists some possible causes of allergic hand dermatitis. Physical Findings. The diagnosis of allergic contact dermatitis is obvious when the area of inflammation corresponds exactly to the area covered by the allergen (e.g., a round patch of eczema under a watch or inflammation in the shape of a sandal strap on the foot). Similar clues may be present with hand eczema, but in many cases allergic and irritant hand eczemas cannot be distinguished by their clinical presentation. Hand inflammation, whatever Nummular Eczema Eczema that appears as one or several coin-shaped plaques is called nummular eczema. This pattern often occurs on the extremities but may also present as hand eczema. The plaques are usually confined to the backs of the hands (Figure 3-24). The number of lesions may increase, but once they are established they tend to remain the same size. The inflammation is either subacute or chronic and pruritus is moderate to intense. The cause is unknown. Thick, chronic, scaling plaques of nummular eczema look like psoriasis; treatment for nummular eczema is the same as that for subacute or chronic eczema. Recurrent Focal Palmar Peeling Keratolysis exfoliativa or recurrent focal palmar peeling is a common, chronic, asymptomatic, noninflammatory bilateral peeling of the palms of the hands and occasionally soles of the feet; its cause is unknown (Figure 3-25). The eruption is most common during the summer months and is often associated with sweaty palms and soles. Some people experience this phenomenon only once, whereas others have repeated episodes. Scaling starts simultaneously from several points on the palms or soles with 2 or 3 mm of round scales that appear to have originated from a ruptured vesicle; however, these vesicles are never seen. The scaling continues to peel and extend peripherally, forming larger, nearly circular areas that resemble ringworm whereas the central area becomes slightly red and tender. The scaling borders may www.PTools.ir