ISTANBUL, TURKEY – Oxidized R-limonene, found in more than 60% of personal care and hygiene products, has been found to be a major cause of fragrance allergy, according to the findings of a large, international, patch test study.
Overall, 5.2% of almost 3,000 patients had a positive patch test result for oxidized limonene, and 37% of those reactions were deemed to be clinically relevant. Shampoos, soaps, perfumes, domestic cleaners, sunscreens, and massage creams are among the household products likely to contain limonene, Dr. Johanna Bråred Christensson said at the annual congress of the European Academy of Dermatology and Venereology. R-limonene is also used in high concentrations in industry as a solvent and degreaser.
R-limonene is structurally a fragrance terpene, with a citrus odor. It is found in nature and produced industrially in mass quantities. In its pure form, R-limonene is nonallergenic or at most a weak allergen. However, when R-limonene is oxidized, it includes limonene hydroperoxides, which Dr. Christensson found to be a contact allergen. This oxidation can occur during storage or handling of R-limonene. The hydroperoxides are often already present in containers of R-limonene when shipped from chemical plants to manufacturers of consumer products, according to Dr. Christensson, a dermatologist at the University of Gothenburg (Sweden).
A stable oxidized R-limonene 3.0% in petrolatum with a controlled 0.33% concentration of limonene hydroperoxides, which is commercially available as a patch test material, was used in the patch test study of 2,900 consecutive dermatitis patients who presented to contact dermatitis clinics in Sweden, Denmark, the United Kingdom, Spain, Australia, and Singapore. Participants completed a questionnaire assessing the relevance of a positive patch test result as indicated by exposure to limonene-containing products on the area of their dermatitis.
The study was funded by grants from national allergy research centers. Dr. Christensson reported having no relevant financial conflicts.