Contact Dermatitis

Basics

Description

  • Irritant:
    • Immediate eczematous eruption (superficial inflammatory process primarily in epidermis)
    • Most common type of dermatitis
    • Trigger substance directly damages the skin resulting in erythema, dryness, cracking, or fissuring; nonimmunologic inflammatory reaction
    • Usually due to repeated exposure to mild irritant (eg, water, soaps, heat, friction, metals)
    • Lesions itch or burn
    • Usually, gradual onset with indistinct borders
    • Most often seen on hands
    • May see vesicles or fissures
    • Dry, red, and rough skin
    • Common irritants include:
      • Cement
      • Hair dyes
      • Wet diapers
      • Rubber gloves
      • Shampoos
      • Frequent hand washing
  • Allergic:
    • Delayed (type IV) hypersensitivity reaction (requires prior sensitization)
    • Allergen-induced immune response
    • Local edema, vesicles, erythema, pruritus, or burning
    • Usually corresponds to exact distribution of contact (eg, watchband)
    • Onset usually within 12–48 hr with prior sensitization; may take 14–21 d for primary exposure
    • Common sources:
      • Nickel
      • Gold
      • Neomycin
      • Bacitracin
      • Preservatives
      • Fragrances
      • Dyes
      • Poison ivy
  • Photocontact:
    • Interaction between an otherwise harmless substance on the skin and UV light
    • Common sources:
      • Shaving lotions
      • Sunscreens
      • Sulfa ointments
      • Perfumes
  • Citrus plants, especially limes and lemons

Pediatric Considerations

  • Allergic contact dermatitis is less frequent in children, especially infants
  • Major sources of pediatric contact allergy:
    • Metals, shoes, preservatives, or fragrances in cosmetics, topical medications, and plants
    • Diaper dermatitis: Prototype for irritant contact dermatitis in children
  • Circumoral dermatitis (perioral dermatitis): Seen in infants and small children; may result from certain foods (irritant or allergic reaction)

Etiology

  • Irritant – direct cellular toxicity leading to inflammation and activation of innate immune system
    • Most common (80% of contact dermatitis)
    • Examples:
      • Soaps, solvents
      • Chemicals (aerosolized pesticides)
      • Certain foods
      • Urine, feces
      • Diapers
      • Continuous or repeated exposure to moisture (hand washing)
      • Coarse paper, glass, and wool fibers
      • Shoe dermatitis: Common; identify by lesions limited to distal dorsal surface of foot usually sparing the interdigital spaces
      • Cement (prolonged exposure may result in severe alkali burn)
      • Solvents, epoxy
      • Chemicals in rubber (eg, elastic waistbands) or leather
  • Allergic – type IV delayed hypersensitivity:
    • Plants, poison ivy, oak, sumac (Rhus dermatitis):
      • Most common form of allergic contact dermatitis in North America
      • Direct: Reaction to oleoresin urushiol from plant
      • Indirect: Contact with pet or clothes with oleoresin on surface or fur or in smoke from burning leaves
      • Lesions may appear up to 3 d after exposure with prior sensitization (12–21 d after primary exposure) and may persist up to 3 wk
      • Fluid from vesicles is not contagious and does not produce new lesions
    • Oleoresin on pets or clothes remains contagious until removed
    • Ragweed pollen
    • Metals (especially nickel, gold)
    • Lotions, cosmetics
    • Topical medications (eg, neomycin, hydrocortisone, benzocaine, paraben)
    • Some foods
    • Ability to respond to certain antigens is probably genetically determined
  • Photodermatitis:
    • UV light changes substances into allergens resulting in an inflammatory reaction (frequently plant sap)
    • Typically no response in absence of sunlight

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