CD05: Retrospective analysis of patch testing in patients with leg ulcer

Dushyanth Gnanappiragasam and Graham Johnston

University Hospitals of Leicester NHS Trust, Leicester, UK

Patients with leg ulcers are reported to be at an increased risk of developing allergic contact dermatitis (ACD) due to the chronic course of this condition, damage to the epidermal barrier, and the use of multiple topical medicaments and occlusive dressings. Traditionally, allergic contact dermatitis of the legs has been most reported to fragrances, antimicrobials, preservatives and rubber accelerators. As a result, the Scottish Intercollegiate Guidelines Network (SIGN)/the National Institute for Health and Care Excellence (NICE) have recommended that periulcer skin should be treated routinely with bland emollients. They recommend dressings that have not been reported as frequent sensitizers, including paraffin gauze, zinc paste, alginates and paraffin-based emollients, and rubber-free compression bandages and stockings. We carried out a retrospective analysis of patients with leg ulcers who attended for patch testing from 2009 to 2021 at a single teaching hospital in the Midlands, UK, to look at whether the prevalence of ACD has changed since the introduction of this guidance and whether the allergen profile has changed. We identified 4343 patients who underwent patch testing using the British Society for Cutaneous Allergy (BSCA) baseline series in accordance with European Society of Contact Dermatitis protocols. Fifty patients presented with leg ulcers. The age range at presentation was 19–97 years with 90% of the patients aged > 60 years. Twenty-six per cent (n = 13) had ACD, as evidenced by a positive patch test, 10% (n = 5) had irritant contact dermatitis, 56% (n = 28) had endogenous dermatitis and 8% (n = 4) had other causes. In the ACD cohort, 24% of patients (n = 5) had positive reaction to fragrance, 24% (n = 5) to preservatives, 14% (n = 3) to rubber accelerators, 9% (n = 2) to antimicrobials and 29% (n = 6) to other haptens, including colophony. The estimated prevalence of leg ulcers in the UK is between 0·1% and 0·3%, with positive patch tests historically reported in up to 75% of this population. We have shown that the prevalence of ACD in this cohort of patients with leg ulcers has decreased but that the allergens identified and their proportions remained the same. Interestingly, no patients in our cohort tested positive to lanolin. This could be due to decreased referrals from decreased availability of dermatologists, decreased awareness among healthcare professionals (HCPs) treating leg ulcers, or increased use of less sensitizing topical treatments and decreased use of sensitizing antimicrobials, the use of fragrance-free products by HCPs and the use of rubber-free bandaging.