ALTERATIONS IN THE SKIN PHYSIOLOGY 7 ing the loss of water from keratin, or in maintaining the skin's pliability, the application of grease to the living skin does protect against chapping. Likewise, greasy emollients applied to the skin following household use of detergents diminish the degree of roughness, redness, scaling, and fissuring. Weather conditions have also been demonstrated to influence the secre- tion of sebum. Studies by Rothman and Emanuel and Dunner have re- vealed that the lipid barrier is lessened in cold weather because the increased viscosity of the sebum inhibits its expulsion upon the skin. Perhaps this lessemng in amount and protectiveness of the lipid barrier allows a more effective wetting and hydration of keratin by soaps and detergents. If tills is so, •t is likewise possible that the better and prolonged contact betwee• keratin and detergents may predispose to increased desiccation. It •s generally agreed that the state of keratin as influenced by soaps and detergents is of vital importance, for in the final analysis the condition of the keratin determines the degree of desiccation, shedding, and cracking of the skin. ]t is not at all clear as to just how soaps and detergents attack this substance to alter its physiology, but it is recognized that keratin re- quires an optimum hydration fo• its well-being. Insufficient water reten- tion or excessive water imbibition will disrupt its physiologic state. In an effort to more clearly determine the influence of soaps and synthetic deter- gents upon keratin, Van Scott and Lyon recently performed the following experiment. They took samples of: (1) dry powdered plantar keratin (2) dry powdered plantar keratin defatted with ether (3) defatted dry powdered plantar keratin to which human sebum had been added in a 1 per cent final concentration (4) ether-washed powdered human hair and ether-washed powdered human nails, suspending them in 2-cc. portions of 1 per cent solutions of several soap and synthetic detergent products. These samples were then incubated for two hours at 40 ø C., and imme- diately following incubation the SH content was determined. From their work they concluded that, among other factors, the alteration of the keratin molecule is an important mechanism in the production of dermatitis from soaps and synthetic detergents. The alteration of the keratin molecule was believed due to the disruption of certain cross bonds between polypeptide chains by denaturation, leading to the release of sulfhydryl groups. If soaps and detergents chemically interact with keratin and thereby change its chemical and possibly its physical structure, therein may lie a partial explanation of the increased desiccation associated with soap and detergent dermatitis. However, it is difficult to categorically apply in vitro reactions to in vivo responses. Further study is necessary to deter- mine whether these agents actually behave in the same manner on skinwhich is viable and physiologically active. There is no doubt that Van Scott and Lyon will attempt to apply this interesting finding to actual clinical conditions.

8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Another physiologic factor worthy of consideration is the buffering or neutralizing capacity of the skin. The perspiration, fatty acids, and keratin help to maintain the acid pH of the skin surface, which is frequently termed the acid mantle of the skin. Sharlit, Burckhardt, Neuhaus, Piper, Jacobi, Robert, and Jaddou, among others, studied the neutralizing capac- ity of the skin to both acids and alkalies, and while the findings of these studies cannot be categorically applied to all synthetic detergents, they have considerable importance with respect to alkali soaps. Although these investigators differ somewhat with respect to the mecha- nism of neutralization, it is well agreed that the alkaline irritants do stimulate a buffering response by the skin. Some of the conclusions would credit the influence of sweat as the main regulatory mechanism other investigations indicate that when the horny layer becomes thinned or permeable, the main buffering effect stems from the action of CO,. diffusion. Still others of these workers attribute the neutralization to the action of the amino acids derived from keratin and sebaceous material. Regardless of the mecha- nism, it seems physiologically beneficial to maintain an acid mantle of the skin, and if soaps or alkalies remove the lipid and sweat barrier without undue harm, the buffering system remains effective. If, however, the irritant effect of a soap is sufficiently repeated and prolonged to such a de- gree as to promote a lag in the neutralizing system, the alkaline influence predominates. Burckhardt particularly believes that individuals who dis- play an eruptive response to alkali likewise show a deficiency in neutraliza- tion capacity. Rather recently, Haxthausen, in working with metal dermatoses of aller- gic contact origin, found that he could sensitize individuals to nickel and cobalt more readily when the skin was in an alkaline state. If an alkaline pH is a possible requisite or an assisting mechanism for certain agents such as nickel and cobalt, it raises the question of whether those individuals who be- come sensitized to soap are among those who show a deficiency in.their neutralizing capacity with a subsequent shift to an alkaline state. This brief review of some recent cutaneous physiological data' applic'able to the problem of soap and detergent dermatitis has intended to show that scientific investigations dealing with the physiology of the skin, as with other organs, can be most complex and speculative. The scientist is con- tinually confronted with the fact that conclusions derived from a given laboratory procedure with dead tissue may be completely nullified when actually applied to living skin provided with active circulatory, buffering, protective, and other functions. Nevertheless, it is quite probable that the laboratory will provide the additional details of those reactions which alter the physiology of the skin and thus bring about a clinical picture of derma- titis from soaps and detergents. Once cause and effect have been estab- lished, prevention can then become a practical reality.