Determination of formaldehyde in formaldehyde-releaser patch test preparations

Background: Positive patch test reactions to formaldehyde‐releasers in patients co‐reacting to formaldehyde are often ascribed to formaldehyde allergy. However, the formaldehyde content of patch test materials has not been investigated. Objectives: To demonstrate and quantify free formaldehyde in commercial patch test materials and in prepared aqueous solutions of formaldehyde releasers. Materials: Free formaldehyde was measured by 13C NMR Spectroscopy in (i) all formaldehyde‐releasers in water available from Chemotechnique® and Brial®, (ii) 5 releasers in petrolatum, (iii) 12 prepared aqueous solutions of formaldehyde‐releasers and (iv) water that had been in contact with petrolatum test samples. Results: In none of the five petrolatum test substances was free formaldehyde found. In all nine commercial aqueous patch test substances and 9 of the 12 prepared solutions, free formaldehyde was demonstrated with concentrations ranging from 0.019% to 0.37% (detection limit 0.01%). Contact of the petrolatum test samples with water resulted in the release of formaldehyde. Conclusions: Most aqueous solutions of formaldehyde‐releasers contain free formaldehyde. Petrolatum‐based patch test materials with formaldehyde‐releasers do not contain free formaldehyde, but probably start releasing it upon contact with water. Therefore, in future studies, determination of free and releasable formaldehyde may be preferable.