Formaldehyde and Formaldehyde-Releasers

This chapter in Kanerva’s Occupational Dermatology, 4th edition (2024), discusses contact allergy to and allergic contact dermatitis from formaldehyde and formaldehyde-releasers. Formaldehyde has many applications, which are shown in tabular format in this publication. However, it is a ubiquitous and important allergen. Contact allergy to formaldehyde occurs frequently in women with hand dermatitis. Sensitization may also be caused by occupational exposure to formaldehyde, e.g., in metalworkers, painters, healthcare workers (e.g., nurses, laboratory technicians, embalmers), hairdressers and beauticians, veterinarians and dental personnel, and workers in the food-processing industry. As formaldehyde is widely distributed in the environment, it is difficult to avoid completely. Thus, even in patients actively trying to avoid products containing it, the dermatitis will infrequently heal completely and permanently. In 2013, the advised concentration used for patch testing to detect formaldehyde sensitization was raised from 1% to 2% in water, as the latter may reveal up to 80% more cases of sensitization. Formaldehyde-releasers are chemicals which release formaldehyde as a result of decomposition and/or chemicals synthesized from formaldehyde that may still contain residues of free formaldehyde. There are over 30 formaldehyde-releasers with a wide array of applications; most are used as preservatives in cosmetics, as antimicrobials in metalworking fluids, paint, lacquers, and varnishes or as durable press chemical finishes in textiles. These are shown in this chapter in tabular format with common names, IUPAC names, synonyms, trade names, CAS numbers, and applications. Positive patch tests to formaldehyde-releasers are often accompanied by concomitant reactions to formaldehyde; in these cases, the patch test to the releaser may be the result of an allergic reaction to the formaldehyde, which is present in or released by the donor test material. With the exception of those used in cosmetics (e.g., quaternium-15, imidazolidinyl urea, diazolidinyl urea, DMDM hydantoin, and 2-bromo-2-nitropropane-1,3-diol), there is little published information on the relevance of observed positive patch test reactions to formaldehyde-releasers. Most reactions to releasers used in metalworking fluids appear not to be relevant with the exception of N,N′-methylenebis(5-methyloxazolidine). The presence of formaldehyde-releasers used as durable press chemical finishes in clothes appears to be safe for consumers. None of the formaldehyde-releasers are important causes of occupational allergic contact dermatitis.