Formaldehyde 2% is not a useful means of detecting allergy to formaldehyde releasers- results of the ESSCA network, 2015 - 2018.

Background Studies suggest patch testing with formaldehyde releasers (FRs) give significant additional information to formaldehyde 1% aq. and should be considered for addition to the European baseline series (EBS). It is not known if this is also true for formaldehyde 2% aq. Objectives To determine the frequency of sensitisation to formaldehyde 2% aq. and co-reactivity with FRs. To establish whether there is justification for including FRs in the EBS. Materials and methods A 4-year, multi-centre retrospective analysis of patients with positive patch test reactions to formaldehyde 2% aq. and 5 FRs. Results A maximum of 15067 patients were tested to formaldehyde 2% aq. and at least 1 FR. The percentage of isolated reactions to FR, without co-reactivity to, formaldehyde 2% aq. for each FR were: 46.8% for quarternium-15 1% pet.; 67.4% imidazolidinyl urea 2% pet.; 64% diazolidinyl urea 2% pet.; 83.3% DMDM hydantoin 2% pet. and 96.3% 2-bromo-2-nitropropane-1,3-diol 0.5% pet. This demonstrates co-reactivity varies between FRs and formaldehyde, from being virtually non-existent in 2-bromo-2-nitropropane-1,3-diol 0.5% pet. [Cohen's kappa: 0 (95% CI: -0.02-0.02)], to only weak concordance for quaternium-15 [Cohen's kappa: 0.22 (95% CI: 0.16-0.28)], where Cohen's kappa value of 1 would indicate full concordance. Conclusions Formaldehyde 2% aq. is an inadequate screen for contact allergy to the formaldehyde releasers which should be considered for inclusion in any series dependant on the frequency of reactions to and relevance of each individual allergen. This article is protected by copyright. All rights reserved.