title: Limonene hydroperoxide analogues show specific patch test reactions.
abstract: BACKGROUND
  The fragrance terpene R-limonene is a very weak sensitizer, but forms allergenic oxidation products upon contact with air. The primary oxidation products of oxidized limonene, the hydroperoxides, have an important impact on the sensitizing potency of the oxidation mixture. One analogue, limonene-1-hydroperoxide, was experimentally shown to be a significantly more potent sensitizer than limonene-2-hydroperoxide in the local lymph node assay with non-pooled lymph nodes.
  
  
  OBJECTIVE
  To investigate the pattern of reactivity among consecutive dermatitis patients to two structurally closely related limonene hydroperoxides, limonene-1-hydroperoxide and limonene-2-hydroperoxide.
  
  
  METHODS
  Limonene-1-hydroperoxide, limonene-2-hydroperoxide, at 0.5% in petrolatum, and oxidized limonene 3.0% pet. were tested in 763 consecutive dermatitis patients.
  
  
  RESULTS
  Of the tested materials, limonene-1-hydroperoxide gave most reactions, with 2.4% of the patients showing positive patch test reactions. Limonene-2-hydroperoxide and oxidized R-limonene gave 1.7% and 1.2% positive patch test reactions, respectively. Concomitant positive patch test reactions to other fragrance markers in the baseline series were frequently noted.
  
  
  CONCLUSIONS
  The results are in accordance with the experimental studies, as limonene-1-hydroperoxide gave more positive patch test reactions in the tested patients than limonene-2-hydroperoxide. Furthermore, the results support the specificity of the allergenic activity of the limonene hydroperoxide analogues and the importance of oxidized limonene as a cause of contact allergy.
authors.affiliation: Dermatochemistry and Skin Allergy, Department of Chemistry and Molecular Biology, University of Gothenburg, SE-405 30, Gothenburg, Sweden; Department of Dermatology, Sahlgrenska Academy at University of Gothenburg, 405 30, Gothenburg, Sweden.
authors.forename: Johanna Bråred
authors.initials: JB
authors.lastname: Christensson
authors.forename: Staffan
authors.initials: S
authors.lastname: Hellsén
authors.forename: Anna
authors.initials: A
authors.lastname: Börje
authors.forename: Ann-Therese
authors.initials: AT
authors.lastname: Karlberg
mesh_terms: D000328:Adult; D000081005:Cyclohexane Monoterpenes; D053138:Cyclohexenes / Q000276:immunology* / Q000378:metabolism; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000276:immunology*; D005260:Female; D006801:Humans; D000077222:Limonene; D023441:Local Lymph Node Assay; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D010328:Patch Tests; D013729:Terpenes / Q000276:immunology* / Q000378:metabolism; D055815:Young Adult
chemical_list: D000081005:Cyclohexane Monoterpenes; D053138:Cyclohexenes; D013729:Terpenes; C000593139:limonene-1-hydroperoxide; C000593140:limonene-2-hydroperoxide; D000077222:Limonene
keywords: allergic contact dermatitis; autoxidation; contact allergy; fragrances; hydroperoxides; limonene; patch testing