title: Can contact allergy to p-phenylenediamine explain the high rates of terpene hydroperoxide allergy? - An epidemiological study based on consecutive patch test results.
abstract: BACKGROUND
  Contact allergy to linalool hydroperoxides (Lin-OOHs) and limonene hydroperoxides (Lim-OOHs) is common. Similarly to what occurs with the terpene hydroperoxides, reactive intermediates formed from p-phenylenediamine (PPD) can cause oxidative modifications of tryptophan residues on proteins in mechanistic studies.
  
  
  OBJECTIVE
  To test the hypothesis that patients sensitized to PPD are at increased risk of concomitant reactivity to either of the terpene hydroperoxides, owing to a 'common pathway' of skin protein oxidation.
  
  
  METHODS
  A database study of consecutively patch tested eczema patients (n = 3843) from 2012 to 2015, tested concomitantly with PPD, Lim-OOHs and Lin-OOHs, was performed. Associations were examined by level of concordance and odds ratios (ORs) adjusted for age, sex, and contact allergy to fragrance mix I and fragrance mix II.
  
  
  RESULTS
  Concomitant reactions to PPD were seen in 2.2% of Lim-OOH-positive patients and in 4.9% of Lin-OOH-positive patients. Neither proportion was higher than expected by chance. No association existed between PPD and Lim-OOH patch test reactivity. In a multiple logistic regression analysis, PPD allergy was associated with an insignificantly increased risk (OR 2.11, 95%CI:0.92-4.80) of a positive patch test reaction to Lin-OOHs.
  
  
  CONCLUSIONS
  PPD sensitization cannot explain the high rates of sensitization to Lin-OOHs and/or Lim-OOHs. Contact allergy to oxidized linalool is more strongly associated with fragrance allergy than with PPD allergy.
authors.affiliation: Department of Dermato-Allergology, National Allergy Research Centre, Herlev-Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark.
authors.forename: Niels Højsager
authors.initials: NH
authors.lastname: Bennike
authors.affiliation: Dermatochemistry Laboratory, Institut de Chimie de Strasbourg, University of Strasbourg, 67081 Strasbourg cedex, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Lepoittevin
authors.affiliation: Department of Dermato-Allergology, National Allergy Research Centre, Herlev-Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark.
authors.forename: Jeanne D
authors.initials: JD
authors.lastname: Johansen
mesh_terms: D000080462:Acyclic Monoterpenes; D000328:Adult; D004396:Coloring Agents / Q000009:adverse effects*; D053138:Cyclohexenes / Q000009:adverse effects; D017449:Dermatitis, Allergic Contact / Q000453:epidemiology / Q000209:etiology*; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D000077222:Limonene; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D039821:Monoterpenes / Q000009:adverse effects; D015999:Multivariate Analysis; D010084:Oxidation-Reduction; D010328:Patch Tests; D010655:Phenylenediamines / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D013729:Terpenes / Q000009:adverse effects*
chemical_list: D000080462:Acyclic Monoterpenes; D004396:Coloring Agents; D053138:Cyclohexenes; D039821:Monoterpenes; D010655:Phenylenediamines; D013729:Terpenes; D000077222:Limonene; D006861:Hydrogen Peroxide; C018584:linalool; C029728:4-phenylenediamine
keywords: concomitant reactivity; contact allergy; d-limonene; linalool; p-phenylenediamine; patch testing; terpene hydroperoxides