Patch Test
A diagnostic procedure in which standardized concentrations of potential allergens are applied to the skin under occlusion to identify delayed-type (Type IV) hypersensitivity reactions responsible for allergic contact dermatitis.
Full Definition
Patch testing is the gold-standard investigation for allergic contact dermatitis, involving the application of allergen-impregnated Finn chambers or similar devices to the upper back under occlusion for 48 hours. Readings are performed at 48 and 96 hours (and sometimes at 7 days) using the International Contact Dermatitis Research Group (ICDRG) grading scale, ranging from negative (−) to extreme reaction (++++). Editors must distinguish 'patch test' from 'prick test' (used for IgE-mediated Type I allergy) and 'scratch test.' In editorial practice, 'patch test' is two words and should not be hyphenated except when used as a compound modifier ('patch-test results').
Usage
Usage note: Two words as a noun ('patch test'); hyphenated only as a compound modifier before a noun ('patch-test results'). Always distinguish from prick testing (Type I/IgE-mediated allergy) in clinical documentation.
In Context
- "Patch testing with the European baseline series revealed a positive reaction to nickel sulphate (++) and fragrance mix I (+)." — Allergy clinic report
- "The author wrote 'patch-test' as a standalone noun; the editor corrected this to 'patch test' (unhyphenated) in accordance with house style." — Copy-editing annotation