Low-molecular-weight contact allergens in p-tert-butylphenol-formaldehyde resin

Background: p-tert-Butylphenol-formaldehyde resin (PTBPFR) is a contact allergen that is included in most standard patch test series. This resin consists of a large number of substances most of which are unknown. Objective: The aim of this study was to investigate if allergens in PTBPFR are molecules mainly of low (MW [lt ] 250), medium, or high molecular weight (MW [gt ] 1,000); to isolate and identify some of the low molecular weight components of the resin; and for new substances to determine if these were allergens. Methods: Gel permeation chromatography, patch testing, high-pressure liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectrometry were used. Results: Patch test reactions indicated allergens in low-, medium-, and high-molecular-weights fractions. The strongest patch test reactivity was seen to a medium molecular weight fraction constituting only 6% wt/wt of the resin for 4 of the patients. Two patients reacted positively to low molecular weight fractions, and one of these patients reacted only to these fractions. The following substances were isolated: 4-tert-butyl-[1,2]benzoquinone, 4-tert-butyl-2,6-bis-hydroxymethyl-phenol, 4-tert-butylbenzene-1,2-diol, 4-tert-butyl-2-hydroxymethyl-phenol, 5-tert-butyl-2-hydroxy-3-hydroxymethyl-benzaldehyde, 4-tert-butyl-2-hydroxymethyl-6-methoxymethyl-phenol, and p-tert-butylphenol. Patients reacted positively to 5-tert-butyl-2-hydroxy-3-hydroxymethyl-benzaldehyde and 4-tert-butyl-2-hydroxymethyl-6-methoxymethyl-phenol but not to 4-tert-butyl-[1,2]benzoquinone. Conclusion: Two new allergens in PTBPFR were found: 5-tert-butyl-2-hydroxy-3-hydroxymethyl-benzaldehyde and 4-tert-butyl-2-hydroxymethyl-6-methoxymethyl-phenol.