Allergic Contact Dermatitis: Test and Diagnosis

The history and clinical picture are guideposts for establishing the diagnosis.

2nd-order laboratory parameters-depending on the results of the history, physical examination, and obligatory laboratory parameters-for differential diagnostic clarification.

• Epicutaneous test (synonyms: patch test, patch test) – provocation test (allergy test) used to determine whether contact allergy is presentNote:
  • Children < 6 years: testing selectively with the suspected contact allergens only if contact allergy is strongly suspected.
  • Children < 12 years: test allergens should be applied for 24 hours only.

  Reading times:

  • Tag 0: Stick epicutaneous plaster
  • Day 2 (48 hours): remove patch, first reading.
  • Day 3 (72 h): second reading.
  • Day 7 (168 hours): third reading

  Notice:

  • If the aim is to achieve the highest possible specificity (probability that actually healthy people who do not suffer from the disease in question are also detected as healthy in the test), an exposure period of two days is recommended.
  • If it is a matter of high sensitivity (percentage of diseased patients in whom the disease is detected by the use of the procedure, ie, a positive finding occurs), can be considered to limit the exposure duration to one day.
  • To differentiate a true allergic reaction from increased skin irritation, the detergent sodium lauryl sulfate is co-tested as an irritant control.
  • Medications that should be discontinued before performing the epicutaneous test:
    • Discontinue steroid one week before the epicutaneous test.
    • Antihistamines: discontinue at the interval of 5 half-lives.
• If necessary, skin biopsy (tissue removal from the skin) for histology u. Immunohistology.

For tattooing – use of the standard series of the German Contact Allergy Group (DKG) with the following blocks:

• No. 1 (standard series)
• No. 24 (leather and textile colors)
• No. 37 (Industrial biocides)
• No. 38 (Preservatives, e.g. in externals).
• No. 47 (tattooing agent)

Reading criteria for epicutaneous reactions following the recommendations of the ICDRG (International Contact Dermatitis Research Group).