Patch testing to plants: sensitisation associated with exposure to plants, essential oils and botanicals in cosmetics.

ABSTRACT

BACKGROUND: Contact allergy to plants, particularly Compositae, presents with dermatitis and is diagnosed with skin patch testing. Sesquiterpene lactone mix is a common screening allergen for plant allergy. The rate of plant allergen sensitisation in New Zealand, which is affected by local horticultural factors, has not previously been documented. AIMS: To investigate the rate of plant allergen sensitisation in New Zealand's regional population, characterise common allergens and reassess appropriate allergens for patch testing. METHODS: Retrospective analysis of patient demographics and patch-test results over an eight-year period (2012 to 2020) was performed at a tertiary patch-test clinic in Auckland, New Zealand. RESULTS: 820 patients completed patch testing. There was a 12.9% sensitivity rate (a positive reaction on patch testing) to at least one plant allergen and a 6.2% plant allergy rate (positive reaction of current relevance). The most frequent positive reactions were Myroxylon pereirae (n=38), colophonium (n=35) and sesquiterpene lactone mix (n=14). Of patients with a plant allergy (n=51), the allergy source was a botanical in a cosmetic product in 27 cases (52.9%), a plant in ten (19.6%) and an essential oil in two (3.9%). CONCLUSIONS: Reactions to plant allergens were related to botanicals in cosmetics and creams, plants and essential oils. Rates of plant sensitisation in our cohort are comparable with international data.