CD01 Sensitization to rubber additives: a multicentre British Society for Cutaneous Allergy audit in the UK and Ireland

Abstract

Rubber additives may cause allergic contact dermatitis (ACD) due to widespread presence in consumer and industrial products. The aims of this study were (i) to audit the prevalence of sensitization to rubber additives in the British Society for Cutaneous Allergy (BSCA) baseline series and (ii) to assess sensitization rates to other rubber additives. A retrospective multicentre audit was carried out to analyse patch test results from 3367 consecutive patients in 14 UK or Irish centres from 1 December 2024 to 1 December 2025. The baseline series contains thiuram mix (TM), N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD), mercapto mix (MM), mercaptobenzothiazole (MBT) and carba mix (CM). In total, 612 patients with clinical suspicion of allergy to rubber additives underwent extended rubber series testing. Overall, 156 of 3367 (4.6%) patients tested in the baseline series had at least one positive reaction. Their mean age was 42 years (range 12–81), 57.7% were female and 69.2% had atopy. The hands (n = 95, 60.9%) and face (n = 82, 52.6%) were the most commonly affected sites, with multisite involvement in 83 (53.2%). Exposures included gloves, cosmetic applicators, footwear and sports equipment. CM was the most frequently positive hapten (2.6%), followed by TM (1.9%), MBT (0.4%), IPPD (0.4%) and MM (0.3%). Current relevance was identified in 64% of CM and 77% of TM reactions, with occupational exposure in 58 (78%). In the extended rubber series, 69 of 612 tests were positive for at least one rubber additive. The most frequent allergens were tetraethylthiuram disulfide (TETD; n = 25) and tetramethylthiuram monosulfide (TMTM; n = 20). Two of 25 (8%) and 1 of 20 (5%) patients positive to TETD and TMTM, respectively, were negative to TM. Five of 18 (28%) patients who tested positive to 1,3-diphenylguanidine tested negative to CM. Two-thirds of the most frequently positive allergens not represented by baseline series mixes are also not in the current BSCA rubber series: n-(cyclohexylthio)phthalimide (n = 5) is in the rubber series, but 4,4′-dithiodimorpholine (n = 4) and 4,4′-diaminodiphenylmethane (n = 3) are not. TM and CM remain valuable screening tools. Sensitization to rubber additives not represented in the BSCA baseline series suggests rubber additive allergy may be underdetected. These findings suggest evolving trends in rubber additive use. The BSCA will be updating the current recommended rubber additive series.