Persistence of contact allergy: a retrospective analysis

Area of Science:

• Dermatology
• Allergology
• Immunology

Background:

• Patch testing is crucial for diagnosing allergic contact dermatitis.
• Some positive patch test reactions may not be reproducible upon retesting (non-persistent).
• Non-persistent reactions could indicate initial false positives, leading to unnecessary allergen avoidance.

Purpose of the Study:

• To determine the persistence rates of positive patch test reactions.
• To identify factors influencing reaction persistence.
• To explore allergen-specific differences in persistence.

Main Methods:

• Retrospective analysis of patients patch tested at least twice between 1995 and 2016.
• Included patients with at least one positive, retested allergen.
• Univariable and multivariable analyses assessed factors affecting persistence.

Main Results:

• Of 274 retested positive reactions, 66.8% were persistent.
• Weak positive reactions were significantly less persistent than stronger reactions.
• Metals and fragrances showed lower persistence compared to other allergen groups.

Conclusions:

• Weak positive patch test reactions have a low persistence rate.
• Dermatologists should be cautious when advising allergen avoidance for weak reactions, especially if clinical relevance is uncertain.
• Consideration of allergen group (metals, fragrances) may inform clinical decisions.