Martin Mowitz

Background Contact allergy rates of linalool and limonene hydroperoxides (HPs) have increased. Objectives To demonstrate the patterns of simultaneous positive patch test (PT) reactions and prevalences of multiple contact allergies (MCAs) in patients with contact allergy to linalool and/or limonene HPs. Methods A retrospective analysis of consecutive dermatitis patients in 2015–2020 was performed. Results Of all 4192 patients, 1851 had at least one positive PT reaction. Of these, 410 (22.2%) had MCAs, significantly related to a higher age ( p ‐value = 0.003). Patients with an exclusively positive reaction to linalool HPs but not limonene HPs were shown to have MCAs ( p ‐value <0.001, odds ratio (95% confidence interval) = 4.15 (3.01–5.73)). Patients with simultaneous contact allergies to both linalool and limonene HPs had contact allergies to many other screening and fragrance allergens. Conclusions Simultaneous positive PT reactions to allergens in baseline series and fragrances are common in patients with the HPs contact allergy, especially linalool HPs. The pattern of simultaneous PT reactions principally suggested the co‐sensitization of the cosmetic allergens.

Background Simultaneous overrepresentations of contact allergies and photocontact allergies are common in individuals with photocontact allergy to ketoprofen. Aims To investigate whether contact allergy to oxidised (ox.) geraniol, geraniol, geranial, neral and citral is overrepresented in individuals with photocontact allergy to ketoprofen. Methods The contact allergy rates to ox. geraniol, geraniol, geranial, neral and citral in routinely patch tested dermatitis patients were compared with the corresponding rates in individuals with photocontact allergy to ketoprofen. Results Allergic patch test reactions were noted to ox. geraniol 11% ( n = 39, 5.8%), ox. geraniol 6% ( n = 12, 1.8%), geraniol 6% ( n = 2, 0.3%), geranial ( n = 18, 2.7%), neral ( n = 7, 1.0%) and citral ( n = 15, 2.2%). In those four patients who were diagnosed with photocontact allergy to ketoprofen during the test period, a significant overrepresentation ( p = 0.020) of simultaneous contact allergy to ox. geraniol 11% was demonstrated. Overrepresentation of simultaneous contact allergy to various combinations of ox. geraniol, ox. limonene and ox. linalool was also noted in ketoprofen‐photoallergic patients. Conclusions Contact allergy to ox. geraniol, geranial and citral is common in routinely tested dermatitis patients. There is an overrepresentation of simultaneous contact allergy to ox. geraniol, ox. limonene and ox. linalool in patients with photocontact allergy to ketoprofen.