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BACKGROUND The positivity ratio (PR) and reaction index (RI) characterize the ability of patch-test preparations to produce strong (++ or +++) reactions as opposed to weak (+), questionable, or irritant reactions. OBJECTIVE This study evaluates these measures for North American Contact Dermatitis Group (NACDG) patch-test preparations. METHODS The PR and RI were calculated for 79 NACDG standard allergens tested from 1994 to 2006 (n = 26,479 patients). The median values were used as cutoff values for "acceptable" versus "problematic" preparations. RESULTS The top 10 "acceptable" patch-test preparations (PR 0.46) were mixed dialkyl thioureas 1% in petrolatum (pet), tixocortol-21-pivalate 1% pet, ethylenediamine dihydrochloride 1% pet, sesquiterpene lactone mix 0.1% pet, nickel sulfate 2.5% pet, bacitracin 20% pet, thimerosal 0.1% pet, epoxy resin 1% pet, colophony 20% pet, and mercaptobenzothiazole 1% pet. The most "problematic" patch-test preparations (PR > 55 and RI < or = 0.46) were cocamidopropyl betaine 1% aqueous (aq), benzalkonium chloride 0.1% aq, jasmine absolute 2% pet, iodopropynyl butyl carbamate 0.1% pet, 2-bromo-2-nitropropane-1,3-diol 0.5% pet, methyldibromoglutaronitrile 0.4% pet, methyldibromoglutaronitrile/phenoxyethanol 2% pet and 2.5% pet, dimethylol dihydroxyethyleneurea 4.5% aq, and clobetasol-17-propionate 1% pet. CONCLUSION Caution should be used when interpreting reactions to "problematic" patch-test preparations with a high proportion of weak, irritant, and questionable reactions.

BACKGROUND Identification of putative contact allergen and source material is often done by a combination of patch testing and manufacturer-supplied product information. The accuracy of the identification of allergen-source material and level of allergen in that allergen-source material is not known. OBJECTIVE The objectives of the study were to survey the chemical allergen content of glove allergic contact dermatitis (ACD) patient-identified problem and nonproblem gloves and to evaluate the ability of the patient to discriminate between problem and nonproblem gloves. METHODS Gloves from patch-tested rubber allergen-positive ACD patients were analyzed for species and amount of rubber allergen. RESULTS Approximately half the subjects were able to correctly identify their problem and nonproblem gloves. Correct association of a glove with ACD was directly related to patch-test reaction severity and inversely related to the number of glove brands being used by the patient. Of note, thiurams were not detected in any of the gloves examined. CONCLUSIONS Although patch testing is invaluable in identifying individual allergen sensitivities, the identification of the ACD-causative specific chemical allergen and source material remains problematic. All glove brands used within days prior to and during an ACD episode should be considered potential sources of the contact allergen.

Carvone has occasionally been reported as an allergen, usually in flavorings. Isomers of carvone have been either a mint or a rye flavor and aroma. We report a woman with positive patch-test reactions to carvone (newly added to the North American Contact Dermatitis Group standard series) and dermatitis on the head. She had used a hair conditioner with a "mint" scent, and the dermatitis resolved when she discontinued using this product. While the manufacturer would not confirm carvone as an ingredient, the clinical course, patch-test results, and ingredient list strongly suggest that this was a relevant allergen in this case of allergic contact dermatitis.