Dermatitis, Contact

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 with honey-colored crusting

  • 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

• Herpetic infection

• Cellulitis

• Scabies

• Dermatophytid reaction (allergy or sensitivity to fungi)

• Atopic dermatitis

• Pompholyx

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