Patterns of positive patch test reactions to formaldehyde and formaldehyde releasers at the Finnish Institute of Occupational Health from 2007 to 2020.

BACKGROUND

Formaldehyde is an important contact sensitizer. Formaldehyde releasing substances induce positive reactions in formaldehyde-allergic patients, but there are also reactions independent of formaldehyde allergy. In an earlier study, stronger formaldehyde reactions led to more positive reactions to quaternium-15.

OBJECTIVES

To analyze patterns of positive patch test reactions to formaldehyde and different formaldehyde releasers.

METHODS

Patch test files of 1497 patients investigated during the period November 2007-August 2020 were retrospectively reviewed for positive reactions to formaldehyde and its releasers. During the study period, almost all (≥99.3%) patients were tested with a formaldehyde dilution series and six formaldehyde releasers.

RESULTS

Ninety-three patients tested positive to formaldehyde; 80% of these had positive reactions to at least one formaldehyde releaser, most often benzylhemiformal. There were only nine independent contact allergies to formaldehyde releasers. There were only two reactions to 2-bromo-2-nitropropane-1,3-diol and they occurred in formaldehyde-negative patients. In patients with extreme (+++) reactions to formaldehyde, concomitant positive reactions to any of the other 11 investigated formaldehyde releasers were more common than in patients with milder formaldehyde reactions.

CONCLUSIONS

Strong formaldehyde reactions were associated with positive reactions to formaldehyde releasers.