Cross-reaction patterns in patients with contact allergy to simple methylol phenols

The low-molecular-weight phenols 2-methylol phenol (2-MP), 4-methylol phenol (4-MP), 2,4,6-trimethylol phenol (2,4,6-MP), 3-methylol phenol (3-MP), 2,4-dimethylol phenol (2,4-MP), and 2,6-dimethylol phenol (2,6-MP) are contact sensitizers in resins based on phenol and formaldehyde (P-F-R). Other chemically related low-molecular-weight phenols are common in the environment. In patients hypersensitive to P-F-R and MPs, it is for diagnostic, therapeutic and preventive reasons necessary to know their cross-reaction patterns, which this study was therefore designed to investigate. In patients with contact allergy to a P-F-R and at least 1 MP, additional patch testing was performed with 6 MPs and 13 chemically related compounds. The 19 substances were tested at equimolar concentrations and in serial dilutions. Investigations by high-performance liquid chromatography were carried out to exclude contamination as the cause of the patch test reactions. Probable cross-reacting substances were o-cresol, p-cresol, salicylaldehyde, 2,4-dimethyl phenol, and 2,6-dimethyl phenol.