CORRESPONDENCE March 12, 1955 Mr. Maison G. deNavarre, Chairman, Publications Committee JouRN^[ ov THE SOCIETY OF COSMETIC CHEMISTS 404 Lothtop Road Grosse Pointe Farms 36, Mich. Dear Sir: In the interest of factual accuracy, some of the statements made by Dr. Peck in his paper, "Toxic and Allergic Complications of Hair Dyes," are subject to criticism and correction. I refer here primarily to the chemical aspects of the subject. The use of the expression "para dyes," although current in the hair dye- ing field, is too loose and inaccurate a designation for a scientific paper, when used to describe the oxidation colors or oxidation chromogens. Also, there seems to be some confusion in the author's mind as to what "para dyes" are. On page 118 he states, "Paratoluenediamine, para-amino- phenol, metol (paramethylaminophenol sulfate), and rodiuol (para-amino- phenol hydrochloride) can be used instead of the para dyes. They are less toxic but not as effective as the latter." Actually, the so-called "para dyes" may contain some or all of the com- pounds listed above, with or without p-phenylenediamine. There is no hair dye preparation today which is based solely on p-phenylenediamine. In fact, for some shades it is not necessary to use p-phenylenediamine at all. The patent and other literature has described more than 200 intermediates suitable for use as oxidation hair dyes, and only a small proportion of these are derivatives, homologues or compounds of p-phenylenediamine. It is also a fact that with the present type of hair dye formulations, the amount of p-phenylenediamine used comprises a much smaller proportion of the total amount of intermediates present than was formerly the case. It seems to me that a proper evaluation of toxic and allergic manifesta- tions resulting from hair dyes should include a reasonably accurate knowl- edge of the contents of the products tested. Incidentally, the list of intermediates cited according to Winter contains a number of inaccuracies which could easily have been detected and cor- rected, as for example, calling sulfo-para-aminometacresol (Metol) or sulfo- 2,5-diaminophenol (Areidol). These are but minor and relatively unim- portant instances of the perpetuation of errors through quotations and cita- tions of references without critical study or even examination. Of more importance, perhaps, are some of the errors and inaccuracies dis- closed in his discussion of the manufacture ofp-phenylenediamine, due to Dr. Peck's apparent misunderstanding or misinterpretation of the informa- tion given him. At the present time p-phenylenediamine is made and has been made for 223

224 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS more than forty years by the reduction of p-nitraniline. At a very early period in the history ofp-phenylenediamine, it was made by the reduction of p-amidoazobenzene and it is possible to make it by other methods, in- cluding the direct amination ofp-dichlorobenzene. But so far these meth- ods have had only theoretical interest. The starting material for the manu- facture of p-phenylenediamine is still p-nitraniline. However, the method of making p-nitraniline has undergone important changes in the past generation. Formerly, p-nitraniline was made by the nitration of acetanilide, whereby the p-nitroacetanilide was obtained and mixed with a small proportion of the 0-nitroacetanilide. The nitration product was treated to remove the ortho compound, and was saponified to give p-nitraniline, which was then reduced in the usual manner to give p- phenylenediamine. In some cases, the p-nitroacetanilide was reduced first to p-aminoacetanilide, which was then saponified, forming p-phenylene- diamine. In comparatively recent years, p-nitraniline has been made almost exclusively by the amination ofp-nitrochlorobenzene, whereby it is obtained in a very pure form. Most of the p-phenylene diamine (not all) available today has been puri- fied by vacuum distillation, and is of a high degree of purity. It is very possible that the greater purity of the p-phenylenediamine used today is one of the factors responsible for the reduced incidence of cases of dermatitis resulting from oxidation type hair dyes. Other factors which also may be involved are improved formulations so that the contact of the dye with the skin is reduced by the consistency of the product more rapid action of the dye so that the time of contact is reduced improved quality and stability of the hydrogen peroxide used today, resulting in more efficient oxidation of the dye. With increased knowledge of the chemistry of the oxidation dyes, it is to be expected that improvements will be made which will further reduce the proportion of cases of dermatitis. The oxidation dyes, in spite of intense activity in attempts to supersede them with other types of aniline colors, are still the most effective and most efficient means of producing permanent colors on human hair. Yours truly, WILLIAM E. AUSTIN 2446 University Avenue New York, N.Y.