CD01: An association between tosylamide/formaldehyde resin and formaldehyde contact allergy? Changing trends in allergic contact dermatitis to tosylamide/formaldehyde resin across a 38-year period from a tertiary dermatology centre

S. Ryan,¹ I. White,² J. McFadden² and F. Ferguson²

¹University College London Hospital and ²St John’s Institute of Dermatology, London, UK

Tosylamide/formaldehyde resin (TSFR; CAS 25035-71-6) is a well-recognized cause of contact allergy to nail varnish, particularly in women with facial dermatitis. Historically, the allergen in nail varnish has been considered to be the resin itself, with an undetectable amount of free formaldehyde in dried nail lacquer. Studies between 1996 and 2003 demonstrated rates of contact allergy to TSFR in tested populations of 1–12%; however, recent studies have reported a decline in incidence, with rates of 0–0·9%. We aimed to determine the incidence of TSFR contact allergy in our UK-based tertiary centre from 1980 to 2018. Rates of concomitant contact allergy to formaldehyde and formaldehyde-releasing preservatives included within our extended European baseline series were evaluated. Records of all patients undergoing patch testing by us between January 1980 and December 2018 were retrieved. Those with positive patch-test reactions to TSFR, formaldehyde and any formaldehyde-releasing preservative were extracted. Patch testing was performed with Finn ChambersÒ (Bio-DiagnosticsÒ, Upton upon Severn, UK), latterly IQ ChambersÒ (ChemotechniqueÒ, Vellinge, Sweden), with TrolabÒ (Hermal, Reinbeck, Germany) allergens and, more recently, ChemotechniqueÒ. Readings were on days 2/3 and 4/5, conforming to European Society of Contact Dermatitis guidelines. Statistical analysis was performed with the χ²-test. In total, 21 515 patients were patch tested with TSFR in a face series. Altogether, 298 reactions to TSFR [295 females; mean age 41 years (range 7–86)] were recorded of which 99% (n = 295) were identified between 1980 and 2010 and 1% (n = 3) between 2010 and 2018. The prevalence of TSFR sensitivity from 1980 to 2009 and from 2010 to 2018 was 0·78% and 0·03%, respectively. Thirty-three patients with TSFR contact allergy were also allergic to formaldehyde (P < 0·001). Concomitant sensitization with formaldehyde-releasing preservatives were found: quaternium-15 (8·4%); diazolidinyl urea (3·0%); imidazolidinyl urea (1·3%) and 2-bromo-2-nitropropane-1,3-diol (1·3%). TSFR contact allergy in our UK population has decreased to low levels in the last decade, as also found in similar American and Australian studies. This reflects changing patterns of usage of nail cosmetics, with the increased use of non-TSFR nail polishes and the rising popularity of gel nails. In recent years, a rising incidence of contact allergy to 2-hydroxyethyl methacrylate in gel nails has resulted in its inclusion into the baseline series. The significantly high rate of concomitant contact allergy to formaldehyde in patients with TSFR contact allergy and the decreasing rates of concomitant allergy with formaldehyde releasers suggests that formaldehyde release does play a role in TSFR contact allergy, unlike what has previously been considered.