Pontén, AAalto-Korte, KAgner, TAndersen, KEGimenez-Arnau, AMGonçalo, MargaridaGoossens, AJohansen, JDLe Coz, CJMaibach, HIRustemeyer, TWhite, IRBruze, M2014-04-032014-04-032013Contact Dermatitis. 2013;68(1):50-3.http://hdl.handle.net/10400.4/1674BACKGROUND: The currently used patch test concentration for formaldehyde is 1.0% (wt/vol) in water. However, clinical experience and previous studies suggest that 1.0% might be insufficient for detecting an optimized number of clinically relevant cases of contact allergy to formaldehyde. OBJECTIVES: To validate earlier patch test results for comparison of 1% (wt/vol) and 2% (wt/vol) formaldehyde in water, and to investigate co-reactivity with quaternium-15. MATERIALS AND METHODS: In 12 dermatology clinics, 3591 patients were routinely patch tested simultaneously with 2.0% (wt/vol) (0.60 mg/cm(2)) and 1.0% (wt/vol) (0.30 mg/cm(2)) formaldehyde. Micropipettes were used for delivering the exact dosage of the allergen. RESULTS: Significantly more patients reacted to 2.0% formaldehyde than to 1.0% (3.4% versus 1.8%, p < 0.001). Overall, there were no sex differences between those reacting positively to 2.0% and 1.0%. Of 25 quaternium-15-positive patients, 4 (0.1%) reacted positively without reacting to formaldehyde. CONCLUSION: On the basis of the results of this multicentre study, as well as of previous studies, it can be suggested that 2.0% (wt/vol) in water formaldehyde should be used in routine patch testing in the baseline series.engFormaldeídoTestes CutâneosTestes PatchDermatite de Contacto AlérgicaAlergéniosjournal article