A19. Contact dermatitis

From greek.doctor
  • Contact dermatitis
    • Types
      • Important types
        • Allergic contact dermatitis
        • Irritant contact dermatitis
        • Phototoxic contact dermatitis
        • Photoallergic contact dermatitis
      • Not so important types
        • Seborrheic dermatitis
        • Infectallergic dermatitis
        • Perioral dermatitis
        • Stasis dermatitis
    • Clinical features (rash)
      • Acute
        • “Sunburn type”
          • Erythema
          • Oedema
          • Vesicles
          • Urtica
          • Pruritus
        • “Exanthema type”
          • Macule
          • Papule
          • Plaque
          • Wheal
      • Subacute
        • Erythema
        • Fissure
        • Scaling
      • Chronic
        • Hyperkeratosis
        • Fissure
        • Scaling
        • Lichenification
    • Diagnosis
      • Patch test
        • Contains haptens in patches which are applied to the back
        • Reading at 48, 72, 168 hours
        • Contains common haptens according to European and local standards
          • Cosmetic ingredients
          • Plants
          • Metals
          • etc.
        • + = erythema, oedema
        • ++ = papule, vesicle
        • +++ = bulla, erosion, ulcer
        • Crescendo – reaction worsens with time
          • Typical for allergic contact dermatitis
        • Decrescendo – reaction improves with time
          • Typical for irritant contact dermatiti
    • Treatment
      • Identification of cause
      • Topical
        • Emollients (moisturizers)
        • Corticosteroids
        • Calcineurin inhibitors
      • Systemic
        • Antihistamines
        • Corticosteroids
  • Allergic contact dermatitis
    • Etiology
      • Poison ivy
      • Nickel
      • Chromium
      • Perfumes
      • Soaps
      • Cosmetics
      • Tattoos
      • Latex
      • Rubber
      • Topical medications
        • Budesonid
    • Pathomechanism
      • Type IVa hypersensitivity
      • Mediated by a hapten, which binds to an endogenous protein and becomes an immunogenic allergen
      • The body is sensitized to the allergen upon first contact
      • With repeated contact a rash develops
  • Irritant contact dermatitis
    • Etiology
      • Solvents – remove lipids in the stratum corneum
        • Like alcohol
      • Acids, bases, salts – destroy proteins in the stratum corneum
      • Dust – mechanically destroys stratum corneum
      • Excessive hand washing
      • Mineral oils
      • Detergents
      • Metals
      • Dry air
      • Warm air
      • Cold air
    • Pathomechanism
      • Not immune-mediated
      • Due to direct irritation -> leads to damage of stratum corneum
      • -> release of inflammatory mediators
  • Phototoxic contact dermatitis
    • More common than photoallergic type
    • Etiology
      • Topical
        • Bergamot
        • Psoralen (in plants)
        • Tar
      • Systemic
        • Tetracycline
        • Sulphonamides
        • Quinolones
        • HCTZ
    • Pathomechanism
      • UV radiation converts a photosensitive molecule into a cytotoxic one
    • Only occurs on sun-exposed skin
    • Phototoxic contact dermatitis is exploited in psoralen-UVA (PUVA) treatment
  • Photoallergic contact dermatitis
    • Less common than phototoxic type
    • Etiology
      • PABA
      • Perfumes
      • Aromatic oils
      • Benzocaine
    • Pathomechanism
      • UV radiation converts a photosensitive molecule (a photoallergen) into an allergen -> type IV hypersensitivity
    • Only occurs on sun-exposed skin