The use of carvone in consecutive patch testing.

BACKGROUND: Carvone (l-carvone) is a mint-tasting flavour additive that most of us is exposed to and can cause allergic contact reactions. OBJECTIVES: To analyse the frequency and the relevance of positive carvone reactions in a dermatitis population. METHOD: A retrospective analysis of dermatitis patients consecutively tested with carvone from 2017 to 2021. Data were retrieved from the department's patch-test database. RESULTS: Of 3554 patients tested with carvone, 28 (0.79%) had a positive reaction. Carvone-positive patients had higher mean age, were significantly more likely female (p < 0.001) and had often an intraoral/lip involvement (p < 0.001). In the carvone-positive group, 50% (n = 14) had a relevant reaction, and in 4 of 14, the relevance was first revealed after test reading. Of the carvone-positive patients, 18 of 28 did not have a coexisting allergy to a fragrance/flavour allergen and of these 44% had a relevant allergy. CONCLUSIONS: The study suggests that a significant fraction of relevant carvone contact allergies may be overlooked if the allergen is not tested. Furthermore, as the exposure is widespread, inclusion of carvone in the Swedish baseline series may be justified even if the contact allergy prevalence is below 1%.

Use test with l-carvone in toothpaste on sensitized individuals.

BACKGROUND: The mint flavour carvone (l-carvone) is considered a weak contact allergen. However, contact allergy to carvone is more prevalent in patients with oral lichen planus or oral lichenoid lesions (OLP/OLL). OBJECTIVE: Our aim was to investigate how carvone affects sensitized individuals through a use test with toothpaste containing carvone. Non-flavoured toothpaste served as control. METHODS: Subjects were patch tested prior to the use test-14 subjects allergic to carvone (11 with OLP/OLL), 20 subjects with OLP/OLL and 3 healthy controls. The month-long use test comprised of using toothpaste twice daily. Subjects were examined fortnightly. Clinical signs were assessed with a mucosal scoring system. The subjects' oral health-related quality of life was measured with the oral health impact profile (OHIP-49). RESULTS: Local reactions to the carvone toothpaste presented as aggravated OLL (7/10) and peri-oral eczema (2/10) in allergic subjects. They also had significantly higher mucosal and OHIP scores compared with those receiving non-flavoured toothpaste. CONCLUSION: In sensitized individuals, oral exposure to carvone gives aggravated oral lesions and/or peri-oral eczema. The lesions mimic OLP and allergic individuals are therefore at risk of not being assessed with regard to flavour contact allergy.

Carvone Contact Allergy in Southern Sweden: A 21-year Retrospective Study.

Carvone (l-carvone), a mint flavour in spearmint oil, is considered a mild skin sensitizer. Carvone-sensitization may be linked to oral/perioral signs and oral lichen planus, but studies are sparse. The prevalence of patch test reactions to carvone and relevant findings from the positive group were investigated. Records for patch-tested patients at the Malmö clinic, for the period 1996 to 2016, were studied. Carvone-positive and carvone-negative patients were compared regarding patch test data from baseline series and dental series. Dental series-tested carvone-positive patients were also compared with a matched group. A total of 147 out of 4,221 referred patients had a positive patch test to carvone. Sensitized patients had higher mean age and were primarily women; 73% had oral signs and 57% had oral lichen. Concomitant patch test reactions to gold, nickel and mercury were common. In the matched group-comparison carvone-positive patients had a higher frequency of oral lichen, but no difference was found in sensitization to gold and mercury.

Quantification of l-carvone in toothpastes available on the Swedish market.

BACKGROUND: Toothpastes have widespread use in the population, and contain flavours to give a pleasant and often minty aroma. Flavours are prevalent allergens in toothpastes, and adverse reactions often present as perioral dermatitis or stomatitis. l-Carvone, a mint flavour found in spearmint oil, is one of these allergens. There are few studies on contact allergy to l-carvone, and some of them have indicated a positive relationship with oral lichenoid lesions. OBJECTIVES: To qualitatively and quantitatively investigate the presence of l-carvone in commercially available toothpastes on the Swedish market. METHODS: l-Carvone in 66 toothpastes was analysed with straight-phase high-performance liquid chromatography. The product labels were studied with regard to limonene. RESULTS: l-Carvone was found in 64 of 66 toothpastes (concentration: 0.00005-0.35%). In 10 of these, the concentration exceeded 0.1%. Higher concentrations of l-carvone were found if limonene was listed on the label. CONCLUSION: The majority of toothpastes on the Swedish market contain l-carvone, but the concentration hardly relates to the advertised flavour or labelled ingredients. It is hitherto unknown whether the found concentrations are sufficient for induction of contact allergy in individuals with healthy oral mucosa or in those with oral lichenoid lesions or other mucosal disease.