Patch testing with a mixture of 2 phenol-formaldehyde resins.

1310 patients were routinely patch tested with a paratertiary-butylphenol-formaldehyde resin (PTBP-F-R), a resol resin based on phenol and formaldehyde (P-F-R-2), and a mixture of these 2 resins. Approximately 2.5 times more patients with contact allergy to phenol-formaldehyde resins were diagnosed when routinely patch tested with P-F-R-2 in addition to PTBP-F-R. Although patch testing with a mixture of both resins was not as good as patch testing with the 2 resins separately, it was better than testing only with PTBP-F-R, since 1.6 times more patients with contact allergy to phenol-formaldehyde resins were still diagnosed. P-F-R-2 is therefore recommended for routine patch testing, preferably as a separate patch test but otherwise as a mixture with PTBP-F-R.

Contact sensitizers in resins based on phenol and formaldehyde.

A paratertiary-butyl phenol-formaldehyde resin is present in the routine patch test series of the International Contact Dermatitis Research Group. This resin was not sufficient to trace patients with contact allergy to resins based on phenol and formaldehyde (P-F-R). A particular resol resin (P-F-R-2) was demonstrated to be a good tracer of patients with P-F-R hypersensitivity. 2-methylol phenol (2-MP), 4-methylol phenol (4-MP) and 2,4,6-trimethylol phenol (2,4,6-MP) were, besides formaldehyde, known sensitizers in P-F-R. The sensitizing potentials were confirmed both in humans and in guinea pigs. Eleven new contact sensitizers in P-F-R were established. A consistently performed patch testing, including testing with serial dilutions of each sensitizer, facilitated comparisons and conclusions concerning (a) assessment of irritancy/allergenicity, (b) determination of highest acceptable contaminations, (c) evaluation of clinical relevance and (d) choice of substances for cross-reactivity testing. Six theoretically possible substances in P-F-R, 3-methylol phenol, 2,4-dimethylol phenol, 2,6-dimethylol phenol, 2,21-dihydroxydiphenyl methane (2,21-HPM), 4,41-dihydroxydiphenyl methane (4,41-HPM) and 2,41-dihydroxydiphenyl methane (2,41-HPM), were established as contact sensitizers and also demonstrated and identified in P-F-R-2. Five sensitizers were isolated from P-F-R-2 and identified to be 4,4-dihydroxy-3-(hydroxymethyl)-diphenyl methane (4,41-H-3-HPM), 4,41-dihydroxy-3,31-di-(hydroxymethyl)-diphenyl methane (4,41-H-3,31-HPM), 4,4-dihydroxy-3,5-di-(hydroxymethyl)-diphenyl methane (4,41-H-3,5-HPM), 2,41-dihydroxy-3,31-di-(hydroxymethyl)-diphenyl methane and 2,4-dihydroxy-31,51-di-(hydroxymethyl)-diphenyl methane. Nine sensitizers, 2-MP, 4-MP, 2,4,6-MP, 2,21-HPM, 4,41-HPM, 2,41-HPM, 4,41-H-3-HPM, 4,41-H-3,31-HPM and 4,41-H-3,5-HPM, were investigated using guinea pigs for sensitizations. The guinea pig maximization test was modified to increase standardization, enable a blind evaluation and also statistical comparisons between test animals and appropriate control animals. All 9 substances, except 4,41-HPM and 2,41-HPM, were established as contact sensitizers in guinea pigs. The 4,41-H-HPM were the most potent allergens. Phenol-formaldehyde resins and products based on P-F-R were investigated for the presence of 14 contact sensitizers. The concentrations varied and the highest concentrations were demonstrated for simple methylol phenols in P-F-R of the resol type.(ABSTRACT TRUNCATED AT 400 WORDS)