Sensitizing capacity of 5,5'-di-tert-butyl-2,2'-dihydorxy-(hydroxymethyl)-dibenzyl ethers in the guinea pig.

In patients hypersensitive to p-tert-butylphenol-formaldehyde resin (PTBP-F-R), it is for diagnostic, therapeutic and preventive reasons necessary to know the identity of the primary sensitizing substances, their sensitizing capacities as well as their cross-reaction patterns. We have recently shown that the 2 dimers in PTBP-F-R, 5,5'-di-tert-butyl-2,2'-dihydroxy-3-hydroxymethyl-dibenzyl ether (X) and 5,5'-di-tert-butyl-2,2'-dihydroxy-3,3'-dihydroxymethyl-dibenzyl ether (IX) are contact sensitizers in man. The aim of this study was to investigate the sensitizing capacities of these dimers in PTBP-F-R and potential cross-reacting substances in the guinea pig with the guinea pig maximization test. IX, X, 2,6-dimethylol-p-tert-butylphenol (2,6-MPTBP), 2-methylol-p-tert-butylphenol (2-MPTBP), p-tert-butylcatechol (PTBC), 5,5'-di-tert-butyl-2,2'-dihydroxy-dibenzyl ether (XI) were used as possible cross reacting substances. IX and X were shown to be sensitizers. When compared to the sensitizers in phenol-formaldehyde resin, IX is a strong sensitizer (p= 0.00052) and X a moderate sensitizer (p=0.0053). Animals sensitized to IX showed cross-reactions to X (p=0.010), 2,6-MPTBP (p=0.0011) and PTBC (p=0.0498). Animals sensitized to X showed no cross-reactions to the substances that were tested. The results indicate that IX is a main allergen in PTBP-F-R, with possibly also X.