Allergic Contact Dermatitis

Aka: Allergic Contact Dermatitis, Contact Urticaria

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II. Pathophysiology

  1. Only occurs in a genetically predisposed person
  2. Type 4 Hypersensitivity Reaction (delayed-type)
  3. Agent specific immunologic cell-mediated response
    1. Requires sensitization
    2. Reaction can be induced by over 3000 chemical agents

III. Course

  1. Develops 24-48 hours after exposure (6 hours to 7 days)
    1. Can develop after years of continued exposure
  2. Resolves after 2-3 weeks after removal of causative agent

IV. Causes: Common

  1. Nickel (less expensive jewelry)
    1. Reaction occurs in 6% of persons exposed
    2. Consider Patch Testing for nickel allergy
    3. Nickel allergic patients can test jewelry for nickel
      1. Spot test is commercially available
    4. Consider irritant dermatitis from jewelry
      1. Remove Jewelry when washing hands
      2. Jewelry traps soap and lotions
  2. Black hair dye
  3. Topical Medications
    1. Mycolog
    2. Neomycin
    3. Benzocaine
    4. Ethylenediamine
    5. Merthiolate (Thimerosal)
  4. Latex Allergy (10-17% of health care workers)
  5. Rhus Dermatitis (reaction in 70% of those exposed)
  6. Cosmetics (Fragrances and preservatives)
  7. Occupational exposures
    1. Potassium dichromate (cement, dyes, textiles)
      1. Welders
      2. Painters, dyers, leather tanners, lithographers
      3. Battery workers
    2. Epoxy resin (adhesives, electrical casings)
      1. High-tech workers (e.g. computers)
      2. Cable workers
      3. Pipe workers
    3. Rosin (adhesives)
    4. Rubber (thiuram, mercaptobenzothiazole, Carbamate)
    5. Surgery and cosmetic (acrylates: methyl methacrylate)
      1. Dentists and Dental Technicians
      2. Orthopedic surgeons
    6. Dyes
      1. Glyceryl monothioglycolate
      2. Para-phenylene diamine (in paint-on Tattoos)
  8. Sports participation
    1. See Sport-related Contact Dermatitis

V. Causes: Tattoo related reactions

  1. Topical Antibiotic reaction (e.g. Neosporin)
  2. Dye reaction
    1. Mercuric Sulfide (Red): Irritant
    2. Cadmium (Yellow): Photo-reaction to sunlight

VI. Symptoms

  1. Severe Pruritus (early symptom)
  2. Mild Pain or burning at dermatitis site

VII. Signs

  1. Sharply demarcated lesion in region of topical agent exposure
    1. Distribution is single most important clue
  2. Characteristics
    1. Marked local erythema and edema (differentiate from Cellulitis)
    2. Lesions may have drainage with crusting
    3. Papules or Vesicles may occur
    4. Skin may appear scaled, thickened or atrophic in longstanding exposure
  3. Numerous Vesicles
    1. Contrast with Pustules in Irritant Contact Dermatitis

VIII. Differential Diagnosis

  1. See Annular Lesion
  2. Cellulitis
  3. Irritant Contact Dermatitis
  4. Atopic Dermatitis or nummular Eczema
  5. Localized Psoriasis
  6. Squamous Cell Carcinoma

IX. Diagnostics

  1. Consider in atypical cases without obvious cause
  2. Patch Test (preferred, performed by allergists)
  3. Lesion Skin Biopsy
    1. Epidermal Spongiosis
    2. Spongiotic Vesicles
    3. Infiltrating Lymphocytes

X. Management

  1. Withdraw offending agent
  2. Localized Allergic Contact Dermatitis
    1. Topical Corticosteroids (e.g. Triamcinolone cream 0.1%)
    2. Topical Tacrolimus
  3. Widespread involvement
    1. Systemic Corticosteroids (see Rhus Dermatitis for example protocol)
  4. Refractory cases (typically via dermatology or allergy referral)
    1. Phototherapy
    2. Systemic Immunosuppressants (e.g. Methotrexate, Cyclosporine)

XI. Resources

  1. Haz-Map (Occupational Exposure Database)
    1. http://www.haz-map.com

XII. References

  1. Habif (1996) Clinical Dermatology, p. 84-94
  2. Lushniak (2000) Prim Care 27(4):895-916 [PubMed]
  3. Peate (2002) Am Fam Physician 66(6):1025-40 [PubMed]
  4. Owen (2018) Am J Clin Dermatol 19(3): 293-302 [PubMed]
  5. Vedela (2022) Am Fam Physician 106(6): 709-10 [PubMed]

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