The following article requires a subscription:



(Format: HTML, PDF)

Background: The oxidized forms of the fragrance terpenes limonene and linalool are known to cause allergic contact dermatitis. Significant rates of contact allergy to these fragrances have been reported in European studies and in a recent worldwide study. Patch testing to oxidized terpenes is not routinely carried out either in the U.K. or in other centres internationally.

Objectives: To investigate the prevalence of contact allergy to oxidized limonene and linalool in the U.K.

Methods: Between 1 August 2011 and 31 December 2012, 4731 consecutive patients in 13 U.K. dermatology departments were tested for hydroperoxides of limonene 0[middle dot]3% pet., hydroperoxides of linalool 1[middle dot]0% pet., stabilized limonene 10[middle dot]0% pet. and stabilized linalool 10[middle dot]0% pet. Doubtful (? ) and equivocal ( /-) reactions were grouped together as irritant reactions.

Results: Two hundred and thirty-seven patients (5[middle dot]0%) had a positive patch test reaction to hydroperoxides of limonene 0[middle dot]3% pet. and 281 (5[middle dot]9%) to hydroperoxides of linalool 1[middle dot]0% pet. Irritant reactions to one or both oxidized terpenes were found in 242 patients (7[middle dot]3%). Eleven patients (0[middle dot]2%) had a positive patch test reaction to the stabilized terpenes alone.

Conclusions: This large, multicentre U.K. audit shows a significant rate of allergy to the hydroperoxides of limonene and linalool plus a high rate of irritant reactions. Testing to the oxidized forms alone captures the majority (97[middle dot]0%; 411 of 422) of positive reactions; testing to nonoxidized terpenes appears to be less useful. We recommend that the hydroperoxides of limonene and linalool be added to an extended baseline patch test series.

What's already known about this topic?:

* Limonene and linalool auto-oxidize upon exposure to air and their oxidation products can cause contact allergy.

* A significant rate of allergy to oxidized limonene and linalool has been shown in multicentre European studies and one small, single-centre U.K. study.

What does this study add?

* This is the first multicentre audit to show a significant rate of allergy to oxidized terpenes throughout the U.K.

* There is a high rate of irritant reactions to the oxidized terpenes.

* We recommend that oxidized limonene and linalool be added to an extended baseline patch test series in the U.K.

* The optimum concentration of the terpene hydroperoxides for patch testing has yet to be determined.

(C) 2014 British Association of Dermatologists