POTENTIAL UTILITY OF ION-EXCHANGE RESINS 261 can be mixed intimately without losing their original identities. For ex- ample, a strongly basic anion exchanger and a strongly acidic cation ex- changer can be combined and neutralization does not occur, at least when the size of the resin particles is greater than colloidal in dimension. Each material retains its original identity in the mixture until a solution of an ionized salt comes in contact with the resin combination. Thus, if aqueous sodium chloride is' added to a mixture of strongly acidic and strongly basic resins, the sodium is exchanged for hydrogen on the cation exchanger, and the chloride is exchanged for hydroxide on the anion exchanger. The re- sult of this reaction is the formation of the sodium salt of the cation ex- changer and the chloride salt of the anion resin with the simultaneous pro- duction of water. The resin salts remain insoluble and from all outward appearances the combination is unchanged, except possibly for a slight change in volume. In recent years the novel properties of ion exchange materials have re- ceived considerable attention in the pharmaceutical field, where they are the active ingredients in antacid formulations, sodium reduction compounds intestinal absorbents, gastric indicator reagents, etc. They also are being used as carriers or depot agents for various drugs such as p-aminosalicylic acid, amphetamine, caprylic acid, etc. With the development of all of these therapeutic compounds, the acute and chronic toxicity of a wide variety of ion exchange resins, both acidic and basic types, has been checked. The work of Martin (2), Root (3), Heming (4) and McChesney (5) contains pertinent information on the pharmacological properties of these materials. IoN EXCHANGE RESINS IN ANTIPERSPIRANT-DEODORANT FORMULATIONS This review of the physical and chemical characteristics of •on exchange resins serves as background for a discussion of the applicability of these products to cosmetic formulations, particularly antiperspirant-deodorant preparations. In the course of a general investigation of the chemistry of perspiration, Thurmon and Ottenstein (6) first proposed that a weakly acidic ion exchange resin might be useful in controlling or preventing the formation of some of the malodorous constituents of apocrine sweat. After considerable orientation work, Thurmon and co-workers demonstrated that a fine particle size, carboxylic acid type cation exchanger, when combined with a mild astringent, aluminum sulfocarbolate, and suspended in a suit- able hydrophilic vehicle such as glyceryl monostearate showed promise as an antiperspirant-deodorant (7). Clinical evidence was obtained which indicated this combination possessed some apparent advantages over a widely used commercial antiperspirant-deodorant cream. The important advantages observed in this study are as follows:

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