Contact allergy to phenol-formaldehyde resins

Adverse reaction to phenol‐formaldehyde resins include depigmentation, irritant dermatitis, chemical burns and allergic contact dermatitis. Allergic contact dermatitis from phenol‐formaldehyde resin has mainly been ascribed to resins based on paratertiary‐butyl phenol and formaldehyde, and such a resin is included in the ICDRG standard patch test series, based on phenol and formaldehyde, 26 patients were positive to at least 1 resin. The figures for positive reactions to paratertiary‐butyl phenol‐formaldehyde resin and the 2 other resins were 0.8%, 1.0% and 3.0% (440 tested subjects), respectively. Therefore, a battery of phenol‐formaldehyde resins should be used for screening purposes, since patch testing with the paratertiary‐butyl phenol‐formaldehyde resin is not sufficient to identify patients with contact allergy to phenol‐formaldehyde resins. Several of the 26 patients were patch tested with the basic substances phenol, formaldehyde and paratertiary‐butyl phenol, but only 1 positive reaction to formaldehyde was noted. The sensitizing capacity of 2‐methylol phenol, 4‐methylol phenol and 2,4,6‐trimethylol phenol, all 3 compounds being possible ingredients of resins based on phenol and formaldehyde, was demonstrated; 5 of 14 resin positive patients reacted to at least 1 of these methylol phenols.