No abstract

Background: There is an ongoing discussion on whether routinely patch testing with pphenylenediamine (PPD) 1.0% pet. is safe, owing to the risk of patch test sensitization. Lateappearing 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 PPDsensitized 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.active sensitization, allergic contact dermatitis, contact allergy, delayed, dilution series, falsenegative reactions, hypersensitivity, late-appearing patch test reactions, PPD

Many protective gloves used by hairdressers are unsuitable for protection against the risk of elicitation of allergic contact dermatitis caused by PPD.