title: Optimizing the patch-test concentration of para-tertiary-butylcatechol: results of a prospective study with a dilution series.
abstract: Para-tertiary-butylcatechol (PTBC), which has long been patch tested internationally at 1% and 0.5% concentrations, was recently shown to induce patch-test sensitization at the 1% patch-test concentration. In order to determine a safe patch-test concentration, we performed a prospective study with lowered patch-test concentrations. A dilution series of PTBC 0.25%, 0.1%, 0.01% and 0.001% (petrolatum, pet.) was tested on the upper back. Additionally, 0.25% PTBC was tested on the left upper arm to allow patients to carry out self-examination daily. Patch tests were read on D1-3, D7, D14 and D21 after patch-test application. Patients who were not able to return for all scheduled readings were telephoned and asked to report any reaction at the patch-test sites. 65 out of the 101 patients included completed the study. A positive patch-test reaction was observed in 4 patients during D1-D3, indicating previous sensitization. 1 patient had a doubtful reaction at D3 reading. Negative patch-test results were noted in 60 patients. None of the patients developed a positive patch-test reaction during the late readings (D7-D21). Thus, patch-test sensitization was not observed in any case. Para-tertiary-butylcatechol 0.25% pet. is recommended for patch testing internationally.
authors.affiliation: Department of Dermatology, University of Essen, Medical School, Hufelandstr 55, 45122 Essen, Germany. uwe.hillen@uni-essen.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Hillen
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Frosch
authors.forename: Tom
authors.initials: T
authors.lastname: Franckson
authors.forename: Claudia
authors.initials: C
authors.lastname: Pirker
authors.forename: Manfred
authors.initials: M
authors.lastname: Goos
mesh_terms: D000328:Adult; D000485:Allergens / Q000737:chemistry; D002396:Catechols / Q000737:chemistry; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000592:standards*; D011446:Prospective Studies
chemical_list: D000485:Allergens; D002396:Catechols; C038096:tert-butylcatechol