III. Efficacy: Evaluating Allergic Contact Dermatitis

IV. Technique

  1. Place drop of each diluted agent in patch test chamber
  2. Apply patch to non-irritated, clean skin of back
  3. Outline each patch outline with pen
  4. Label agent locations on skin and in medical record
  5. Remove patch in 48 hours
  6. Measure skin reaction (see below)

V. Approach: Interpretation of skin test

  1. Erythema: 1+
  2. Edema or Vesicles involve <50% of patch area: 2+
  3. Edema or Vesicles involve >50% of patch area: 3+

VI. Causes: False positive (consider if multiple positives)

  1. Hyperirritability of skin
  2. Contaminant irritant or allergen on tested skin
  3. Reaction to tape holding patch in place
  4. Irritant Contact Dermatitis
    1. Reaction resolves more quickly than in allergy
    2. Burning sensation contrasted with itching in allergy
    3. Sharply demarcated reaction

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