Sensitivity to hair dyes

Abstract Patch tests with oxidation (para-) hair dyes were made on 1,024 hospitalized male and female patients. Black hair dyes having the highest concentration of aromatic diamines were used. Two black hair dyes, one based on paraphenylenediamine and the other on paratoluylenediamine, were selected. Controls with the dye base which contained soaps, detergents, ammonia, resorcinol, and solvents were consistently negative. So far as could be ascertained, none of the persons, especially those found sensitive to the dyes, had used hair dyes previously. Of the eight persons found sensitive, three (0.29 per cent) reacted only to the black hair dye based on paraphenylenediamine, four (0.39 per cent) reacted only to the black hair dye containing paratoluylenediamine, and one (0.10 per cent) reacted to both dyes. Age seemed to be related to incidence of sensitization. Only one person of the 516 patients 50 years old or younger was found to be sensitive to the paraphenylenediamine hair dye. The remaining seven reactors were over 50 years of age and their positive skin tests with hair dyes might have been due to cross-sensitization to related compounds. In our experiments, two of four sensitive persons tested gave positive skin reactions with 2 per cent aqueous procaine solution. The patch test is essential, therefore, to any person contemplating hair dyeing. The erythema in the positive cases was evident twenty-four hours after the application of the test solution, and in no instance was an increased or delayed reaction observed after forty-eight hours. The skin tests were repeated at intervals of from three to four weeks, once on 301 persons and twice on sixty-seven persons, including the eight sensitive persons. No change developed in the specificity of the reaction of persons sensitive to one or the other type of hair dye and no positive reaction appeared in previously negative cases. In the only patient under 50 years of age who was found to be sensitive to the dye, early repetition of the tests gave weaker reactions and repetition on three occasions a year later gave negative results. The chemical composition of the presently used hair dyes, as well as the mechanism of the conversion of the para compounds into hair coloring pigments, is discussed.