CD08 The fine print in topical anti-inflammatories: excipient exposure in topical corticosteroids and calcineurin inhibitors

Abstract

Allergic contact dermatitis associated with topical corticosteroids (TCSs) and topical calcineurin inhibitors (TCIs) may result from sensitization to the active drug or to excipients within the vehicle. UK-specific data on excipient-related allergen exposure in these preparations are limited. We aimed to characterize excipient exposure in UK TCS and TCI preparations and map these excipients to recognized contact allergens included in the recommended British Society for Cutaneous Allergy (BSCA) patch test series. A cross-sectional review of UK-available TCS and TCI preparations listed in the Electronic Medicines Compendium was conducted in October 2025. Excipients were extracted from product monographs to Microsoft Excel, and analysed descriptively. In total, 105 topical preparations were identified (67 single-agent TCSs, 35 combination products and 3 TCIs). Overall, 103 unique excipients were identified. The mean number of excipients per preparation was 6 (range 1–15). Vehicle formulation strongly influenced excipient burden, with creams containing a higher mean number of excipients (9, range 5–15) than ointments (3, range 1–7). Excipients represented within the BSCA baseline and medicaments patch testing series included emollients such as cetyl, stearyl or cetostearyl alcohols (n = 45) and lanolin (n = 7). Emulsifiers and preservatives within these series included propylene glycol (n = 30), chlorocresol (n = 23), parabens (n = 10) and sorbitan sesquioleate (n = 3). Ingredients represented within the BSCA facial series included benzyl alcohol (n = 8), triethanolamine (n = 3) and propyl gallate (n = 2). Other excipients not routinely tested within recommended BSCA series included polyethylene glycol alkyl ethers (n = 27), beeswax (n = 13), castor oil (n = 4), antioxidants including all-rac-α-tocopherol (n = 12), butylated hydroxytoluene (n = 11) and butylhydroxyanisole (n = 4), and the solvent hexylene glycol (n = 6). These findings characterize excipient composition in UK topical anti-inflammatories. While many excipients are represented within BSCA patch test series, others are not routinely tested. This survey identifies candidate excipients for future BSCA audits, supporting refinement of the BSCA medicaments series and excipient-aware prescribing to guide choice of formulation after patch testing.