Concentration variability of potent allergens of p-tert-Butylphenol-formaldehyde resin (PTBP-FR) in patch test preparations and commercially available PTBP-FR.

Background: p-tert-Butylphenol-formaldehyde resin (PTBP-FR) is a common component of glues used in the manufacturing of many plastic, electronic, rubber, wood, and leather products. Two main allergens of PTBP-FR have been described. Objectives: The objective of this study is to determine the concentrations of the two main allergens of PTBP-FR in diagnostic patch testing preparations and PTBP-FR available to glue and adhesive manufacturers. Methods: Nuclear magnetic resonance spectrometry (NMR) was used to confirm identity and determine the purity of reference materials. High-pressure liquid chromatography (HPLC) was used to analyse patch test preparations and commercially-available PTBP-FR. Results: In the PTBP-FR in analysed patch test preparations the highest concentration of the allergenic dimer 4-tert-butyl-2-(5-tert-butyl-2-hydroxy-3-hydroxymethyl-benzyloxymethyl)-6-hydroxymethylphenol found was 1.79% and the lowest 0.21%. The highest concentration of the allergenic dimer 4-tert-butyl-2-(5-tert-butyl-2-hydroxy-benzyloxymethyl)-6-hydroxymethylphenol found in PTBP-FR of analysed patch test preparations was 0.50% and the lowest concentration found was 0.04%. In commercially-available PTBP-FR the highest concentration of -tert-butyl-2-(5-tert-butyl-2-hydroxy-3-hydroxymethyl-benzyloxymethyl)-6-hydroxymethylphenol found was 3.7% and the highest concentration of 4-tert-butyl-2-(5-tert-butyl-2-hydroxy-benzyloxymethyl)-6-hydroxymethylphenol found was 1.1%. In three PTBP-FR samples neither allergen could be detected. Conclusions: Our data suggests that reporting resin concentration in petrolatum is not predictive of a consistent concentration of the two main allergens of PTBP-FR. The ten-fold difference in allergen concentration between different patch test preparations has significant ramifications for maintaining consistent dose of delivered allergen. The results of this study reinforce the need for patch test product standardization in the Contact Dermatitis community.