Download Allergic Contact Dermatitis Nummular Eczema Recurrent Focal

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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
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