CD02 Contact allergy to formaldehyde and formaldehyde releasers: a UK and Ireland multicentre audit

Abstract

Formaldehyde and formaldehyde releasers are widely used preservatives in cosmetic, household and industrial products, remaining well-recognized causes of allergic contact dermatitis. We aimed to audit the frequency and clinical relevance of patch test positivity to formaldehyde releasers in the British Society for Cutaneous Allergy (BSCA) baseline and supplementary series. A retrospective multicentre audit was carried out across 12 UK and Irish centres. This included 3118 consecutive patients patch tested to the BSCA baseline series between 1 December 2024 and 1 December 2025. Baseline formaldehyde releasers included formaldehyde 2.0% aqueous, 4-tert-butylphenol formaldehyde resin (PTBP) 1.0% in petrolatum (pet.), Quaternium-15 1.0% pet., 2-bromo-­2-nitropropane-1,3-diol 0.5% pet., imidazolidinyl urea 2.0% pet., diazolidinyl urea 2.0% pet., and methyldibromoglutaronitrile (MDBGN) 0.3% pet. Nine centres tested selected patients to supplementary formaldehyde releasers. Patch test positivity to at least one baseline formaldehyde releaser was identified in 201 of 3118 patients (6.4%). Their mean age was 44 years (range 5–82), 75% were female and 69% were atopic. The most frequently affected sites were the face (108, 53.7%), hands (96, 47.8%) and legs (39, 19.4%). Implicated sources included hair products, topical medicaments, household cleaners, cosmetics and textiles. The most frequently positive baseline formaldehyde releasers were formaldehyde and MDBGN (both 1.3%), followed by 2-bromo-2-nitropropane-1,3-diol (1.2%), Quaternium-15 (0.9%), diazolidinyl urea (0.6%), imidazolidinyl urea (0.3%) and PTBP (0.3%). Current relevance was highest for Quaternium-15 (48.1%) and 2-bromo-2-nitropropane-1,3-diol (39.5%), followed by formaldehyde (35.0%), imidazolidinyl urea (30.0%), diazolidinyl urea (26.3%), MDBGN (17.5%) and PTBP (12.5%). Occupational relevance was identified in 6.0%. Supplementary series testing identified additional low-frequency-positivity to toluenesulfonamide formaldehyde resin (6 of 1445, 0.42%) and DMDM hydantoin (2 of 1421, 0.14%). Formaldehyde, 2-bromo-2-­nitropropane-1,3-diol, Quaternium-15 and diazolidinyl urea remain currently important haptens. MDBGN showed low current relevance despite a 1.3% positivity rate, consistent with declining sensitization following legislative bans in 2008. Inclusion of MDBGN and other formaldehyde releasers within the baseline series warrants review. With Quaternium-15 being prohibited in cosmetic products in the UK since 2019, future reaudit would be valuable.