[Diagnosis of contact allergy in practice using current guidelines]

Area of Science:

• Dermatology
• Allergology
• Immunology

Background:

• Contact allergy management relies on allergen avoidance due to lack of causal therapy.
• Unidentified allergens lead to persistent dermatitis, significantly impacting patient quality of life.
• Patch testing is the gold standard for diagnosing contact sensitization.

Purpose of the Study:

• To present key practical aspects of patch testing for contact allergens and drugs.
• To update and enhance the German patch test guideline based on a systematic literature review.

Main Methods:

• Summarized current consensus guidelines for patch test procedures.
• Conducted a supplementary selective literature search.
• Updated the German patch test guideline (AWMF registry no. 013-018, 2019).

Main Results:

• Routine testing includes baseline series, special series, and patient-specific preparations.
• A new evidence-based recommendation is late reading (7-10 days) to avoid missing reactions.
• Antihistamines should be stopped 5 half-lives prior to testing; strip patch testing is advised for suspected false-negatives.

Conclusions:

• Guideline-based patch testing should be performed early for all suspected contact allergies.
• Targeted patch testing effectively identifies relevant allergens.
• This approach guides further systematic investigations for accurate diagnosis and management.