Tapinarof as a Likely Contact Allergen: Evidence From Patch Testing of Allergic and Irritant Contact Dermatitis

Background: Tapinarof cream 1% is a novel, non-steroidal topical aryl hydrocarbon receptor-modulating agent approved for the treatment of plaque psoriasis and atopic dermatitis (AD). There has only been one report of allergic sensitization to tapinarof cream. Objectives: This study aimed to determine whether tapinarof cream-induced contact dermatitis represents an allergic or irritant reaction, and to identify the causative allergen in allergic cases. Patients/Methods: Nine patients (seven with psoriasis and two with AD) who developed contact dermatitis during treatment with tapinarof cream were included. Patch testing was performed with the cream as is; tapinarof at concentrations of 1%, 0.3%, and 0.1% in petrolatum; and two additives (propylene glycol 10% aqueous solution and disodium edetate hydrate 1% in petrolatum). Results: Patch testing with tapinarof cream as is was positive in four patients with psoriasis and both patients with AD. All six patients also showed dose–response relationships with tapinarof, increasing from 0.1% to 1%. The remaining three patients with psoriasis showed negative patch test results to both the cream as is and its individual components. Conclusions: Tapinarof cream-induced contact dermatitis may present as either an allergic or irritant reaction. In all six allergic cases, tapinarof was strongly suggested to be the causative allergen.