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

• 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