Patch testing with limonene and linalool hydroperoxides: higher yield with higher concentrations in a multicenter...

Limonene hydroperoxides (Lim-OOHs) 0.2% and 0.3% and linalool hydroperoxides (Lin-OOHs) 0.5% and 1% are terpenes included in the Spanish standard and extended series. The use of both concentrations is currently being evaluated in clinical practice.

To evaluate the performance of both concentrations in consecutive patch testing of patients evaluated at dermatology centers in Spain reporting to the Spanish Contact Dermatitis and Cutaneous Allergy Research Registry (REIDAC).

A multicenter, cross-sectional, observational study was conducted. Clinical and demographic characteristics were described for patients consecutively patch tested with limonene hydroperoxides (0.3% and 0.2%) and linalool hydroperoxides (1% and 0.5%) between January 2019 and December 2024. Patch test results were analyzed for each concentration, and their usefulness in clinical practice was assessed.

Among the 10,502 patients included, the frequency of positive reactions was 2% and 4.1% to Lim-OOHs 0.2% and 0.3%, respectively, and 2.9% and 5.3% to Lin-OOHs 0.5% and 1%, respectively. The higher concentrations detected a greater number of positive, doubtful, and irritant reactions, with low concordance between concentrations. The loss of positive cases when using only the higher concentrations was limited, and the detection efficiency of the lower concentrations was low.

Lim-OOHs 0.3% and Lin-OOHs 1% showed better diagnostic performance, with a limited loss of clinically relevant cases, and could therefore be considered more appropriate for the assessment of contact dermatitis caused by these hydroperoxides.