88 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS flow of perspiration, is not altogether impossible. Moreover, there exists some direct pertinent evidence: The experiments carried out by Richard- son and Meigs (8), with the aid of an ingenious yet simple measuring de- vice, indicate that an effectively performing aluminum salt can reduce perspiration markedly on a treated skin area, as compared with the un- treated control area. It might be interposed that the latter observations apply to eccrine sweating only. However, since eccrine as well as apocrine glands occur in the axillary area, the inhibition of eccrine sweat alone would reduce the total output. Of course, this concession is made only for the sake of argument, since the experiments of Richardson and Meigs certainly do not preclude the possibility of a comparable response being given by the apocrine secretion. Other relevant evidence may be found in a paper by Hopf (9). This author attributes to a 15 per cent aluminum chloride solution the capacity for marked reduction of axillary perspiration and odor. No other alumi- num salt tested was found to approach the chloride in efficacy when applied either in solution or in the form of a commercially available (in West Ger- many) cosmetic preparation. This action of aluminum chloride is of short duration, at first, owing to its interruption by the flow of perspiration which may be stimulated by bodily activity, and particularly by heat producing food intake however, following repeated application, its effect is said to become more lasting so that eventually it suffices to make the application only once a week or even less frequently, depending upon the individual case. As to the indirect applicable data, the follo .wing are deemed to be worthy of interest: The protein coagulating potential of the aluminum salts depends upon the anion, as shown by Govett and deNavarre (10) by means of in vitro experiments employing egg white as the protein. The inorganic salts, viz., the nitrate, the chloride, the chlorohydrate and the sulfate of alumi- num were found to be powerful coagulants, while the organic lactate and citrate are weaker in action the phenol sulfonate (or sulfocarbolate) oc- cupies an intermediate position. A method, similar in principle, but employing the coagulation of Ham- marsten's casein, is that of Christian and Jenkins (11) who applied it to a comparative study of aluminum salts. Incidentally, a new aluminum salt, viz., aluminum methionate, 'Al•[(SO3)•CH2]•, was tested by this method with iatisfactory results as to the likelihood of antiperspirant efficiency and comparative harmlessness to fabrics. Other indicative evidence for the coagulant and, therefore, potentially constrictive action of aluminum salts is furnished by experiments on shrink- age of frog skin and on its permeability to water. With aluminum sul- fate and chlorohydrate applied in concentrations ranging from 1 to 15 per cent it was found that, depending upon the concentration, there was a

ASPECTS OF ANTIPERSPIRANTS AND DEODORANTS 89 marked shrinkage of this skin, also a decrease of the osmotic flow through it. Urakame and Christian (12) adapted radioactive tracer techniques to permeability studies on frog membranes in an attempt to obtain correla- tion with astringent and antiperspirant efficacy. For the sake of completeness of record, it should be mentioned here that a protein precipitant is not eo ipso an acceptable antiperspirant, as has been demonstrated by Brun and Manuila (6) in the case of such typical agents as phosphotungstic, sulfosalicylic and tannic acids. At any rate, the available experimental evidence tends to suggest that the action upon the axillary skin area of the so-called astringent aluminum salts is more a matter of degree of effect, rather than one of a categorical assertion or denial of the existence of such an effect. It is unfortunately true that there is no published account of a truly accurate evaluation of the relative antiperspirant effects of the various astringent salts, although some recently published methods endeavor to approach this ideal (13, 14). There is another point to be considered here. In formulating an anti- perspirant preparation, the cosmetic chemist cannot simply aim for com- plete prevention of axillary sweating because this might be concomitant with two undesirable qualities, viz., those of skin irritancy and fabric cor- rosion. There is reason to believe that, other things being equal, the high acidity which certain aluminum salts generate through hydrolysis, viz., with a pH level of the order of 2 to 2.5, would make them effective perspira- tion inhibitors, if applied directly. It is certainly not claimed that the ductal closure effected by means of strong mineral acids, as observed by Hurley and Shelley (7), is a case in point, yet it seems fair to suggest that a systematic study of the effect upon the patency of the ostia of different acids at different pH levels, and of protein coagulant metal salts at different acid reactions, might be worth undertaking in order to bring more clarity into this as yet rather obscure domain. While it is not considered to be the purpose of this presentation to go into details of the formulation ofantiperspirants, some general comments on this subject may be in order (15). The metal salts used most frequently in the formulation of perspiration- inhibiting preparations are those of aluminum and zinc, either singly or in combination. Theoretically, salts of certain other metals could also be employed were it not for their tendency to causing discoloration of the skin and of fabrics (as, e.g., in the case of ferric and chromic salts), or for the risk ofpercutaneous toxicity (as, e.g., in the case of lead and mercuric salts). As for the anion portion, the sulfate, the chloride, the chlorohydrate (also known as the chlorhydroxide), the sulfamate, the phosphate and the phe- nolsulfonate are represented most frequently, though the formate, acetate, lactate, acetotartrate and others are encountered occasionally in actual usage, or in technical and patent references.