Epikutantest

Epikutantest, also known as an epicutaneous or patch test, is a diagnostic procedure used to identify substances that cause allergic contact dermatitis. Standardized allergen preparations are applied to the skin, typically on the upper back, under occlusion for about 48 hours. After removal, the skin is examined at 48 hours and again at 72 hours (and sometimes at 96 hours) to detect delayed hypersensitivity reactions.

Indications for testing include suspected allergic contact dermatitis based on exposure history, occupational dermatitis, or dermatitis related to cosmetics, fragrances, metals (such as nickel), preservatives, rubber accelerators, hair dyes, and certain medications. Patch testing helps distinguish allergic from irritant dermatitis and guides avoidance strategies.

Procedure and materials involve using standardized panels, such as European baseline series or commercially prepared TRUE Test kits, containing a defined set of common contact allergens. Allergens are applied to the back in small chambers or patches and kept in place with adhesive tape. Patients are advised to avoid certain systemic or topical medications that may alter test results and to follow specific aftercare instructions, including avoiding wetting the area before readings.

Interpretation is based on the International Contact Dermatitis Research Group criteria, assigning scores from negative to various positive grades (eg, +, ++, +++), reflecting the intensity and morphology of reactions such as erythema, edema, vesiculation, and papules. A positive result indicates sensitization to a substance, but clinical relevance must be assessed against current exposures.

Limitations include false positives from irritant reactions, false negatives due to recent dermatitis, incomplete allergen panels, and the need for expert interpretation. Management centers on eliminating or reducing exposure to identified allergens and providing alternatives.