4 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS diffusion and retention, sebum, C02 diffusion, and possibly enzyme systems are influenced by external contactants such as detergents. While the physiology of the skin is by no means completely understood, several outstanding contributions in the past fifty years have clarified many of the complexities concerning its structure, function, and reactivity. These data have become standard references for dermatologic investiga- tions, because they contain invaluable background information which will help to explain the cutaneous alterations believed to be attributable to soaps and detergents, among other common contactants. The purpose of this presentation, then, is to review some of the knowledge which has contributed to a better understanding of the physiologic response of the skin to the action of soaps and detergents. Dermatitis caused by detergents of natural or synthetic nature is the result of either low-grade primary irritation or specific sensitization, or at times a combination of both. Most investigators in this field believe that the irritant effect is the most common mechanism and that allergic contact type sensitization is relatively infrequent. This belief has been borne out by the observations of Lane, Blank, Burckhardt, Pluss, Johnson, Kile, Kooyman, and others. Further recognition and acceptance of the primary irritant effect as the major mechanism has been brought about by the use of the patch test. Properly performed patch tests with soaps and detergents have repeatedly demonstrated that specific sensitization to these agents is by no means a common occurrence. It is well established that the primary irritant can injure the integument, but how can we apply this premise to the chemical action of detergents upon the skin ? When irritants contact the human skin so as to alter its physi- ology in one or more ways, the resultant conditions are manifested by cer- tain subjective and objective phenomena. Subjectively, there may be a sense of tightness, dryness, drawing, burning, tingling, itching, or even pain of the affected parts. Objective phenomena or signs as distinguished from subjective symptoms can be readily observed. These include redness, dry- ness, scaling, fissuring, swelling, vesiculation, and sometimes widespread eczematous response. The severity of response usually parallels the con- centration of the irritant and the duration of exposure. All of these physio- logic alterations can be associated with the action of soaps and synthetic detergents, but it is more common to observe redness, dryness, and scaling than to note the more severe effects such as fissuring, vesiculation, or wide- spread eczema. As a group, cutaneous irritants of organic or inorganic nature can be classified according to their effects as follows: 1. Fat removers. 2. Sweat neutralizers.

ALTERATIONS IN THE SKIN PHYSIOLOGY $ 3. Keratin reducers. 4. Keratin stimulators. 5. Protein precipitators. 6. Desiccators. 7. Oxidizers. 8. Hydrolyzers. Though we cannot readily apply all of these effects to the problem of de- tergency, certain of them, such as fat solvency, sweat neutralization, and keratin alteration, have long been associated with the cutaneous action of soaps and detergents. We know that solvents, soaps, and synthetic detergents are able to dis- solve or emulsify lipids and thereby remove them from the skin. The natural lipid material, known as sebum, is a secretory product of the sebaceous glands which is extruded through the hair follicle orifices to form a thin waxy film upon the skin surface. According to Rothman, the protec- tive action of this lipid film against water and water-soluble materials is one of hindering the wetting and penetration of the horny layer. He be- lieves, however, that this role has been overemphasized and that the film is not the only factor which protects the skin against water and water-soluble materials. It has long been held that whenever the skin became dry, or roughened, or cracked, it did so because the lipid content had in some way been dimin- ished. There seems to be no question that the defatted skin surface is more dried and roughened than the normally fatted surface, but the exact role of sebum in maintaining the soft, pliable condition of the skin is not com- pletely understood. It is possible that the layer of sebum may definitely assist in providing a feeling of smoothness, but the recent work of Irvin Blank has introduced a new concept regarding skin pliability. Blank found that the water content of keratin is far more significant in maintaining its pliability than the action of fats and oils. By using cornified epithelium (dried brittle callus from the plantar surface of the foot), and allowing it to remain in contact with lanolin, petrolatum, and natural glycerides of fatty acids lot months at normal or elevated temperatures, he noted that the callus repeatedly failed to soften. However, when the dried brittle callus, under the same conditions, was allowed to absorb a little moisture, it soon became sott and pliable. Further, by taking skin and removing the surface lipids, as described by Winson and Burch, he was able to corroborate their finding that the re- moval of the surface lipid did not increase the rate of water loss from the specimen. This served to indicate that there is no lipid layer acting as a barrier to water loss. On the other hand, when the skin is thoroughly ex- tracted with an ether-alcohol mixture for five days and then allowed to ab-