262 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (a) Less "reactive." (Fewer cases of irritation.) (b) Greater duration of effect. (Less "fugitive" than conventional preparations.) (c) Less damaging to wearing apparel. (d) More effective buffering action in the optimum pH range of 5.0-6.0. Following Thurmon's initial proposals, he launched an investigation of ion exchange resins in the treatment of other dermatological disorders, in- cluding fungus infections, and skin irritations arising from plant irritants, chemical reagents, etc. (8, 9). Thurmon's group also continued their in- vestigation of the chemistry of perspiration, and in 1954 published the re- sults of studies on the adsorption of amino acids and bacterial or fungal metabolites, present in human perspiration, by a combination of cation and anion exchange resins (10). These observations came to the attention of the Japanese investigator, Ikai, who investigated a series of cation and anion exchange resins, singly and in combination, in the adsorption of malodorant products in axillary perspiration (11). Ikai's work is significant in that he carried his studies to the clinical stage and described several formulations which were quite effective as deodorants, particularly mixtures of cation and anion exchang- ers. Ikai suggested that such combinations as Amberlite XE-98 (IRA-411) and XE-64, and IRA-410 and XE-64 in vehicles such as polyethylene glycol ointment, stearyl alcohol emulsion, white petrolatum or methyl cellulose gave optimum results. A condensed summary of Ikai's clinical observations on various resin formulations appears in Table 2. TABLE 2--DEODORIZING EXPERIMENTS ON SUBJECTS WITH PREPARATIONS OF ION EXCHANGE RESINS (IN SPRING)* Vehicle Appraisement for the Presence of the Axillary Odors -After Application • After 12 hr. After 24 hr. After 72 hr. P.E.G.-Ointment 5(-) 3(-) 2(4-) 5(-3-) 11(-) 8(4-) (in summer) White Petrolatum, 5(-) 4(-) 1(4-) 2(4-) 3(-3-) Stearyl Alcohol, Methyl Cellulose 5(-) 3(-) 2(4-) 5(-3-) * Summary of information published in )t. Invest. Dermat. 23, No. 6, 411 (1954). When interpreting the results of this interesting series of experiments, Ikai proposed that the deodorant action of the various resin combinations was due almost entirely to their ability to adsorb basic and acidic compo- nents of apocrine sweat which, according to Shelley's studies, are actually the source of perspiration odor. As indicated, some of the various prepara- tions cited in the above table were effective as long as'seventy-two hours. The duration of activity of each exchanger formulation, containing 20 per

POTENTIAL UTILITY OF ION-EXCHANGE RESINS 263 cent by weight resin, seemed to depend primarily on the degree of adherence of the resin combination to the skin, rather than on the ion exchange ca- pacity of the resin mixture. Since the minimum duration of protection was about twelve hours with some of these preparations, it would appear that Ikai's experiments point the way to the formulation of new deodorant prod- ucts with greater effectiveness per application than is possessed by cur- rently available preparations. The foregoing studies are concerned entirely with the deodorizing action of ion exchange resins, singly and in combination. To obtain effective antiperspirant action, it would be necessary to add an astringent such as aluminum chlorhydrate or aluminum sulfocarbolate to the resin formula- tion. Such reagents can probably be combined with the resins by the use of suitable compounding procedures without impairing their adsorption activity. FACTORS AFFECTING COMPOUNDING PROCEDURES In selecting appropriate compounding techniques Gr ion exchange poly- mers, it is necessary to consider the physical and chemical properties which control their ability to adsorb the malodorous components of perspiration. These factors can be seen more clearly by using as a model one of the resin combinations shown to be effective in Ikai's studies. The combination of the carboxylic exchanger, Amberlite XE-64, and the strongly basic quater- nary amine anion adsorbent, Amberlite XE-98 (IRA-411) is a good ex- ample. Amberlite XE-64 is an insoluble polycarboxylic acid type ex- changer produced by the copolymerization of divinyl benzene and metha- crylic acid. It is supplied as a white, free flowing powder having a particle size in the 300-400 mesh range. The physical stability of this exchanger is entirely satisfactory under usual compounding conditions. Amberlite XE-64, as supplied, is in the acid Grin and has an apparent dissociation constant (pK) of about 4.0. This means that the resin does not have appreciable exchange activity below pH 4.0. As the pH of the environ- ment increases, the adsorption activity of the resin also increases. The saturation capacity of Amberlite XE-64 is not attained until the environ- mental pH reaches a value in the range of 10.0-11.0. Such high pH values would be experienced immediately Gllowing the application of an alkali soap to the surface of the skin. As shown previously by the titration curve of a carboxylic exchanger (Fig. 5), a resin such as Amberlite XE-64 pos- sesses high buffering capacity in the pH range of 5.0-6.0. Amberlite XE-98 is now supplied commercially under the designation, Amberlite IRA-411. This quaternary amine polymer is prepared by first copolymerizing styrene and divinyl benzene. The resin beads thus pro- duced are subsequently chloromethylated and then treated with dimethyl- ethanol amine. The resulting quaternary amine exchanger evolves from