Young, E.Andersen, Klaus E.Bruze, MagnusGiménez Arnau, Anna MariaRoss-Hansen, K.Johanssen, Jeanne DuusMadsen, J.T.Zimerson, E.Svedman, Cecilia2019-07-032019Young E, Andersen KE, Bruze M, Giménez-Arnau A, Ross-Hansen K, Johansen JD. Et al. Twenty-eight-day follow-up of patch test reactions to p-phenylenediamine and p-phenylenediamine dihydrochloride: A multicentre study on behalf of the European Environmental and Contact Dermatitis Research Group. Contact Dermatitis. 2019 Jul;81(1):1-8. DOI: 10.1111/cod.132350105-1873http://hdl.handle.net/10230/41916BACKGROUND: There is an ongoing discussion on whether routinely patch testing with p-phenylenediamine (PPD) 1.0% pet. is safe, owing to the risk of patch test sensitization. Late-appearing patch test reactions may reflect patch test sensitization, but may also be attributable to a low degree of pre-existing sensitization. OBJECTIVES: To follow the positive patch test reactions to PPD and its salt PPD dihydrochloride (PPD-DHC) in order to characterize reaction patterns concerning time and dose in PPD-sensitized individuals. METHODS: Volunteers with previous reactions to PPD 1.0% were included and patch tested with PPD and PPD-DHC in equimolar dilution series. There were then seven follow-up visits over a period of 28 days. RESULTS: Twenty-six volunteers completed the study, of whom 23 of 26 (88%) reacted to PPD 1.0%, and 69% reacted to PPD 0.32%. Altogether, 42% and 27% reacted to the corresponding equimolar concentrations of PPD-DHC. After day 7, no new reactions were observed to any concentration tested, either of PPD or of PPD-DHC. CONCLUSION: No late-appearing reactions to PPD or PPD-DHC were observed at any dose. There is a risk of missing contact allergy when the dose is decreased.application/pdfengThis is the peer reviewed version of the following article: Young E, Andersen KE, Bruze M, Giménez-Arnau A, Ross-Hansen K, Johansen JD. Et al. Twenty-eight-day follow-up of patch test reactions to p-phenylenediamine and p-phenylenediamine dihydrochloride: A multicentre study on behalf of the European Environmental and Contact Dermatitis Research Group. Contact Dermatitis. 2019 Jul;81(1):1-8, which has been published in final form at http://dx.doi.org/10.1111/cod.13235. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.info:eu-repo/semantics/articlehttp://dx.doi.org/10.1111/cod.13235PPDActive sensitizationAllergic contact dermatitisContact allergyDelayedDilution seriesFalse-negative reactionsHypersensitivityLate-appearing patch test reactionsinfo:eu-repo/semantics/openAccess