294 JOURNAL OF THE SOCIETY OF-COSMETIC CHEMISTS "•T-•"•.•%T•'L." d,.. ••• .••. /• . ,o R o. N• •N 0 OH Figure 2.•Sketch of cation exchange resin Figure 3. Sketch of anion exchange resin particle in hydrogen form. particle in hydroxyl form. be used to provide protection against skin invasion by bacteria and fungi as well as organic or inorganic materials which bring about an undesirable alteration in skin pH, thereby permitting use in "preventive maintenance" procedures. THERAPEUTIC A. pH Contro/•mberli•e XE-6• •eak/y •cidic, Carboxylic Type, Cation Exchange Resin Thurmon (13, 14) has shown that a single resin component of the car- boxylic acid type when incorporated in a powder, ointment or lotion adjusts or maintains a desired, mild, acid mantle on the skin. When the skin is broken or irritated, it is common for the damaged area to develop al- kalinity. In some cases, skin surfaces become alkaline from the con- AMBERLITE 1•'12 T AMBERLITE CAR80XYLICTYPEL•CHAN•R, ---'-'"""'"• R. + CAPACITY IN MILLIEOU•VALENT$ PER GRAM Figure 4.--Comparison ooe titration curves for suloeonic (IR-]20) and carboxylic (IRC-50) cation exchange resins. I I I I 4o 0 l, H TiTRATiO N IN 1 • KCL SOLUTION. AMBERLITE IR _•'"• • CAPACITY IN M[LLIEOUIVALENT$ Pt8 GRAM Figure 5.--Comparison of titration curves for weak base (IR-4B) and strong base (IRA-400) type anion exchange resins.

RESINS AND THEIR APPLICATION TO DRUG AND COSMETIC PRODUCTS 295 Strongly Atcidic, Sulfonic Type Cation Exchange Resin 1. Exchange of Cations Rz-H + q- Na+C1 - • Rz-Na + q- H•-C1 - 2. Neutralization Rz-H + q- Na•-OH - • Rz-Na + q- H20 14Zeakly Atcidic, Carboxylic Type Cation Exchange Resin 1. Exchange of Cations Rz-H + q- Na+C1 - • Rz-Na + q- H+C1 - 2. Neutralization Rz-H + q- Na+OH - • Rz-Na + q- H20 Figure 6.--Typical Equilibrium Reactions taminating presence of alkaline earth ions or organic bases. Changes in the pH of the skin are also observed in various diseased conditions. The presence of a carboxylic, ion exchange resin provides a source for hydrogen ions, which are released in an exchange reaction with the electrolyte present on the skin. In suspension in an aqueous O. 15M salt solution, the car- boxylic type resin suggested for this purpose is capable of maintaining a pH of between 3.0 and 6.0. The principle of skin pH control by ion exchange has been utilized by Richardson (12) in a topical ointment, containing Amberlite XE-112, a polyacrylic-carboxylic resin, for the treatment of skin lesions and for the prevention of skin damage resulting from the digestion by intestinal juices of skin surfaces after ileostomy operations. In this formulation, the skin pH is lowered to a level between pH 3 and 5 where the digestive action of pepsin, chymotrypsin or trypsin is reduced. B. Bacteriostatic and Fungistatic ztctivity--Cobalt Salts of Carboxylic Resins Another illustration of therapeutic action provided by an ion exchange resin in a formulation is the bacteriostatic and fungistatic activity of the metallic salt from carboxylic acid type, cation exchange resins in topical preparations (15, 16). The cobalt salt of a carboxylic cation exchange resin has been found to be particularly effective in inhibiting the growth of fungi such as trichophyton gypseum and microsporum lanosum. While soluble salts of cobalt similarly exhibit a fungistatic effect, their use has caused some skin reactions. The use of an ion exchange resin salt of cobalt provides gradual release of cobalt ions in the area of the skin eruption, avoiding high local concentration of cobalt ions and attendant skin sensitization. Concentrations of cobalt as low as 0.1 per cent as cobaltous chloride, in the form of an ion exchange complex, have proven effective for the treatment of such dermatological conditions as dermatophytosis, pruritus, seborrheic dermatitis, intertrigo and eczem a.