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 nonimmunologic inflammatory reaction with erythema, dryness, cracking, or fissuring
    • Usually due to repeated exposure to mild irritant (e.g., 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 (e.g., 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

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: Seen in infants and small children; may result from certain foods (irritant or allergic reaction)

Etiology

  • Irritant (80% of contact dermatitis), e.g.:
    • 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 (e.g., elastic waistbands) or leather
  • Allergic:
    • 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 (e.g., neomycin, hydrocortisone, benzocaine, paraben)
    • Some foods
    • Ability to respond to certain antigens is probably genetically determined
  • Photodermatitis:
    • Inflammatory reaction from exposure to irritant (frequently plant sap) and sunlight
    • Typically no response in absence of sunlight

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