Recommendation to test limonene hydroperoxides 0.3% and linalool hydroperoxides 1.0% in the British Baseline patch test series

Background: There is a significant rate of sensitisation worldwide to the oxidised fragrance terpenes limonene and linalool. Patch testing to oxidised terpenes is not routinely carried out; the ideal patch test concentration is unknown.

Objectives: To determine the best test concentrations for limonene and linalool hydroperoxides, added to the British baseline patch test series, to optimise detection of true allergy and minimise irritant reactions.

Methods: During 2013-2014, 4563 consecutive patients in 12 UK centres were tested to hydroperoxides of limonene in petrolatum (pet.) 0.3%, 0.2% and 0.1%, and hydroperoxides of linalool 1.0%, 0.5% and 0.25% pet. Irritant (IR) reactions were recorded separately from doubtful (?+) reactions. Concomitant reactions to other fragrance markers and clinical relevance were documented.

Results: Limonene hydroperoxide 0.3% gave positive reactions in 241 (5.3%) patients, irritant reactions in 93 (2.0%) and doubtful reactions in 110 (2.4%). Linalool hydroperoxide 1.0% gave positive reactions in 352 (7.7%), irritant reactions in 178 (3.9%), and doubtful reactions in 132 (2.9%). 119 patients with crescendo reactions to 0.3% limonene would have been missed if only tested with 0.1%. 131 patients with crescendo reactions to 1.0% linalool would have been missed if only tested with 0.25%. In almost two-thirds of patients with positive patch tests to limonene and linalool the reaction was clinically relevant. The majority of patients did not react to any fragrance marker in the baseline series.

Conclusions: We recommend that limonene hydroperoxides be tested at 0.3% and linalool hydroperoxides at 1.0% in the British baseline patch test series.