Patch testing with oxidized R-(+)-limonene and its hydroperoxide fraction.

Area of Science:

• Dermatology
• Allergology
• Environmental Health

Background:

• R-(+)-limonene is widely used in consumer products and fragrances.
• While non-oxidized limonene is not allergenic, its autoxidation products are significant environmental allergens.
• Contact allergy to oxidized limonene is a growing concern in occupational and domestic settings.

Purpose of the Study:

• To investigate the prevalence and causative allergens of contact allergy to oxidized R-(+)-limonene.
• To evaluate the efficacy of different patch test preparations for diagnosing limonene allergy.
• To provide clinical support for the classification of oxidized limonene as a skin sensitizer.

Main Methods:

• Patch testing of 2273 patients across four European dermatological clinics.
• Two-step testing involving oxidized R-(+)-limonene, limonene hydroperoxides, limonene oxide, and carvone.
• Evaluation of reaction frequencies and concomitant allergies to other fragrance materials.

Main Results:

• Positive patch test reactions to oxidized R-(+)-limonene varied between 0.3% and 6.5% across clinics.
• Limonene hydroperoxides were identified as the most potent allergens within the oxidation mixture.
• A significant proportion (57%) of limonene-allergic subjects did not react to standard fragrance markers.
• 3% oxidized R-(+)-limonene in non-stabilized petrolatum proved most suitable for diagnosis.

Conclusions:

• Oxidized R-(+)-limonene, particularly its hydroperoxide fraction, is a clinically relevant contact allergen.
• Standard fragrance series may not detect all cases of limonene-induced contact allergy.
• Specific patch testing with oxidized limonene is crucial for accurate diagnosis and management of skin sensitization.