Linalool – a significant contact sensitizer after air exposure

Authors

  • Johanna Bråred Christensson,

    Corresponding author
    1. Department of Dermatology, Sahlgrenska University Hospital, Gothenburg
    2. Dermatochemistry and Skin Allergy, Department of Chemistry, University of Gothenburg, Gothenburg
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  • Mihály Matura,

    1. Dermatochemistry and Skin Allergy, Department of Chemistry, University of Gothenburg, Gothenburg
    2. Unit of Occupational and Environmental Dermatology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm
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  • Birgitta Gruvberger,

    1. Department of Occupational and Environmental Dermatology, Lund University, Malmö University Hospital, Malmö, Sweden
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  • Magnus Bruze,

    1. Department of Occupational and Environmental Dermatology, Lund University, Malmö University Hospital, Malmö, Sweden
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  • Ann-Therese Karlberg

    1. Dermatochemistry and Skin Allergy, Department of Chemistry, University of Gothenburg, Gothenburg
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  • Conflicts of interest: Magnus Bruze is a member of the Research Institute for Fragrance Materials (RIFM) Expert Panel (REXPAN).

Johanna Bråred Christensson
Department of Dermatology
Sahlgrenska University Hospital
413 45 Gothenburg
Sweden
e-mail:johanna.brared-christensson@vgregion.se

Abstract

Background: Linalool is a widely used fragrance terpene. Pure linalool is not allergenic or a very weak allergen, but autoxidizes on air exposure and the oxidation products can cause contact allergy. Oxidized (ox.) linalool has previously been patch tested at a concentration of 2.0% in petrolatum (pet.) in 1511 patients, and 1.3% positive patch test reactions were observed.

Objective: To investigate the optimal patch test concentration for detection of contact allergy to ox. linalool.

Methods: Four concentrations of ox. linalool (2.0%, 4.0%, 6.0%, 11.0% pet.) were tested in 3418 consecutive dermatitis patients.

Results: Ox. linalool 2.0%, 4.0%, 6.0%, and 11.0% pet. detected positive patch test reactions in 0.83%, 3.2%, 5.3%, and 7.2% of the tested patients, respectively. The doubtful reactions increased with rising concentrations but relatively less, giving 5.1%, 6.4%, and 7.3% doubtful reactions, respectively, for ox. linalool 4.0%, 6.0%, and 11.0% pet. Few irritative reactions were seen.

Conclusions: Raising the patch test concentration for ox. linalool gave a better detection of contact allergy, as many as 5–7% positive patch test reactions were detected. We suggest a patch test concentration of ox. linalool 6.0% pet. for future patch testing, giving a dose per unit area of 2.4 mg/cm2 when 20 mg test substance is tested in small Finn Chambers®.

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