CD23 Carvone contact allergy: a case series from a tertiary dermatology service

Abstract

Carvone, also known as 2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one, is a terpenoid compound found naturally in several essential oils. It is also an additive found in mint-flavoured oral hygiene products, toothpastes, mouthwashes and chewing gum. Literature on its clinical relevance and exposure patterns is limited, and awareness remains low. Our aim was to describe the clinical characteristics, exposures, presentations and patch test findings of patients patch tested to carvone in the dental series over a 7-year period. Between 2019 and 2026, we retrospectively reviewed a database at a tertiary cutaneous allergy service of patients patch tested for the dental series containing carvone. Of 636 individuals, three tested positive for carvone. For all, patch testing was conducted to the British Society for Cutaneous Allergy (BSCA) standard series and also to the departmental cosmetic and dental series. Patient records were obtained and data collected on age, sex, presenting symptoms, relevant medical history, medications and exposure history. Three patients (two female, one male; aged 41–76 years) tested positive to carvone at a concentration of 5% in petrolatum. Presentations included dysgeusia (n = 1), temporomandibular joint dysfunction (n = 1) and recurrent lateral tongue ulcers (n = 1). All had prior exposure to carvone-containing products identified from their history. Two patients also tested positive to palladium and sodium tetrachloropalladate(Ii) hydrate, and one of these two also tested positive to nickel sulfate. The third patient tested positive for sodium meta­bisulfite alongside carvone. Carvone is a rare, but clinically relevant contact allergen that may cause persistent cutaneous or oral symptoms. A thorough exposure history is crucial, particularly relating to dental and essential oils. Dermatologists should consider carvone patch testing in patients with unexplained oral, perioral or facial dermatitis. Increased awareness of this allergen since the BSCA added carvone to its facial series, when last updated in 2021, should facilitate earlier diagnosis, targeted avoidance and improved outcomes.