Updated: 9/23/2017

Contact Dermatitis

Review Topic
  • A 3-year-old boy presents to his pediatrician's for a rash on his left lower leg. He had been playing in a wooded area yesterday. He reported a very itchy rash on his left lower leg since this morning. On exam, there are erythematous papules and vesicles in a linear pattern, as though he had brushed something. He is given topical corticosteroids and reassurance.
  • Clinical definition
    • erythematous and pruritic rash caused by cutaneous exposure to
      • allergens
        • most common form of contact dermatitis
      • irritants
        • often involves hands
        • often from occupational exposures
  • Epidemiology
    • prevalence
      • 15-20%
    • demographics
      • female > male
    • risk factors
      • exposure to potential allergens or irritants
      • occupations with higher risk of contact dermatitis
        • healthcare
        • food production
        • cosmetics
  • Etiology
    • most common allergens include
      • poison ivy 
      • poison oak
      • nickel 
    • most common irritants include
      • chemicals
      • alcohol
  • Pathogenesis
    • allergic contact dermatitis
      • immunologic reaction to allergen causing type IV hypersensitivity reaction
      • delayed T-cell mediated reaction
      • activation of Th1 cells 
      • memory CD4+ cells are created and dermatitis develops upon re-exposure or cross-reaction 
    • irritant contact dermatitis
      • nonimmunologic reaction to substance that causes direct damage to the skin
      • release of inflammatory cytokines activated by non-immune pathways
  • Prognosis
    • typically resolves with treatment
  • Symptoms
    • presents 12-48 hours after exposure to allergen
    • presents minutes to hours after exposure to irritant
    • pruritic
    • burning or stinging
  • Physical exam
    • linear or geometric rash, corresponding to topical exposure, composed of papules and vesicles
      • can progress to blisters and bullae
      • for example, patients allergic to the adhesive in a bandaid will present with a square or rectangular-shaped rash
    • eczematous rash
      • lichenification
      • fissuring
      • scaling
  • Labs
    • none
  • Patch testing to
    • identify potential allergens
    • help prevent future exposures
  • Histology
    • spongiosis 
  • Atopic dermatitis
  • Conservative
    • skin moisturizer
      • indication
        • decrease irritation in nonimmunologic contact dermatitis
  • Medical
    • topical corticosteroids
      • indication
        • localized or mild-to-moderate disease
        • first-line therapy
    • systemic corticosteroids
      • indications
        • widespread or severe disease
        • disease that involves mucosa
  • Secondary bacterial infection

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