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Key Features

Essentials of Diagnosis

  • Erythema and edema, with pruritus, vesicles, bullae, weeping or crusting

  • Irritant contact dermatitis: occurs only in area of direct contact with irritant.

  • Allergic contact dermatitis: extends beyond area of direct contact with allergen; positive patch test.

General Considerations

  • An acute or chronic dermatitis that results from direct skin contact with chemicals or allergens

  • Irritant contact dermatitis

    • Eighty percent of cases are due to excessive exposure to or additive effects of primary or universal irritants such as soaps, detergents, or organic solvents

  • Allergic contact dermatitis

    • Most common causes are poison ivy, oak or sumac; topically applied antimicrobials (especially bacitracin and neomycin), anesthetics (benzocaine); preservatives; jewelry (nickel); rubber; essential oils; propolis (from bees); and adhesive tape

    • Occupational exposure is an important cause

Clinical Findings

Symptoms and Signs

  • Itching, burning, and stinging may be severe in both allergic and irritant contact dermatitis

  • Allergic contact dermatitis

    • Characterized by intense pruritus, tiny vesicles and weepy and crusted lesions in acute phase

    • Lesions consist of erythematous macules, papules, and vesicles; may occur beyond the contact area, distinguishing it from irritant dermatitis

    • Affected area may also be edematous and warm

    • The pattern of the eruption may be diagnostic (eg, typical linear streaked vesicles on the extremities in poison oak or ivy dermatitis)

    • Location will often suggest the cause

      • Scalp involvement: hair dyes or shampoos

      • Face involvement: creams, cosmetics, soaps, shaving materials, nail polish

      • Neck involvement: jewelry, hair dyes

    • Reactions may not develop for 48–72 hours after exposure

  • Irritant contact dermatitis

    • Rash is erythematous and scaly, but less likely vesicular

    • Occurs only in the direct sites of contact with the irritant

    • Resolving or chronic contact dermatitis presents with scaling, erythema, and possibly thickened skin

    • Reactions may develop within 24 hours of contact exposure

Differential Diagnosis

  • Impetigo

  • Scabies

  • Dermatophytid reaction (allergy or sensitivity to fungi)

  • Atopic dermatitis

  • Pompholyx

  • Asymmetric distribution, blotchy erythema around the face, linear lesions, and a history of exposure help distinguish contact dermatitis from other skin lesions

  • The most commonly confused diagnosis is impetigo, in which case Gram stain and culture will rule out impetigo or secondary infection (impetiginization)

Diagnosis

Laboratory Tests

  • Gram stain and culture will rule out impetigo or secondary infection (impetiginization)

  • After the episode of allergic contact dermatitis has cleared, patch testing may be useful if triggering allergen is not known

Diagnostic Procedures

  • If itching is generalized, then consider scabies

Treatment

  • See Table 6–2

  • Vesicular and weepy lesions often require systemic corticosteroid therapy

  • Localized involvement (except on the face) can often be managed with topical agents

  • Irritant contact dermatitis is treated by protection from the irritant and use of topical corticosteroids as for atopic dermatitis

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