CD09 Complexities of contact dermatitis: lessons from a case of concomitant budesonide and propylene glycol sensitivity

Abstract Diagnosing contact allergic dermatitis to topical steroids can be challenging. It is often suspected when symptoms worsen or fail to improve despite proper corticosteroid use. This is further complicated by potential allergies to excipients such as propylene glycol, a common solvent and humectant that enhances drug solubility and bioavailability. We present the case of a 67-year-old woman with facial and hand dermatitis persisting for 30 years, treated exclusively with topical therapies throughout this period. Patch testing was conducted using the British Society for Cutaneous Allergy (BSCA) standard, cosmetic, face, fragrance, bakery, rubber, plant and woods, photosensitizers and steroid series, alongside her personal products. Positive reactions on day 4 included propylene glycol 20%, colophony 20%, jasmine absolute Egyptian, tixocortol-21-pivalate 1% in petrolatum, budesonide 0.01% in petrolatum and mometasone furoate ointment. Of interest, on day 2, an edge effect was noted with budesonide 0.01% in petrolatum, which reached a 3 + reaction by day 4, persisting until day 11. The edge effect phenomenon has been reported with corticosteroids and is an indicator of strong cutaneous immune suppression. Out of 8557 patients patch tested over a 22-year period, 48 tested positive to budesonide (0.56%) and 85 tested positive to propylene glycol (0.57%), with only five patients (0.06%) reacting to both of these simultaneously. Despite their low prevalences, these dual sensitivities can significantly impact treatment choices, requiring careful formulation selection. These findings illustrate the importance of testing both active ingredients and excipients to identify clinically relevant allergens. Topical steroids are categorized into four structural classes (Coopman classification): A, B, C and D (subdivided into D1 and D2), with crossreactivity occurring between groups (Spurr A, Pratt M, Shahrigharahkoshan S. Allergic contact dermatitis to corticosteroids. Curr Dermatol Rep 2021; 10: 140–7). Our patient was advised to avoid class A (tixocortol pivalate) and class B (budesonide) corticosteroids, both of which are included in the BSCA standard series, along with any crossreactive compounds. Safe alternatives were recommended, while propylene glycol-containing products such as Dermovate, Metosyn and Synalar were to be avoided. This case underscores the complexity of managing multiple concurrent contact reactions and emphasizes the need for extended readings to improve detection of corticosteroid groups (Van Amerongen CCA, Ofenloch R, Dittmar D, Schuttelaar MLA. New positive patch test reactions on day 7 – the additional value of the day 7 patch test reading. Contact Dermatitis 2019; 81: 280–7). Vigilant allergen avoidance, individualized treatment plans and education are paramount for optimal management to prevent exposure to such allergens in future treatments.