BEHAVIOUR OF COSMETIC CREAMS, LOTIONS AND OILS ON THE SKIN 43 Zusammenfassung Die eigentiimlichen Konsistenzverh/iltnisse der Seifencremes k6nnen auf die reinen fettsauren Kalisalze wiedergespiegelt werden. Bei hohen Tempera- turen ist die Hydrolyse zwar stark, die festtsauren Salze sind aber ge16st oder ihre Dispersionen klar. Mit sinkender Temperafur werden die Gele zun/ichst fest. Obgleich die Hydrolyse und damit die Bildung saurer Salze etwas nachl/iBt, nimmt deren L6slichkeit so stark ab, dab sie schlieBlich auskristallisieren und die Gelbildung st6ren. Die Mischungen werden wieder weich. 'Uberschfissige Fetts/iuren f6rdern die Bildung saurer Salze und k6nnen dadurch das Auskristallisieren begfinstigen. Elektrolyte k6nnen ebenfalls st6rend in diesen Mechanismus eingreifen. •Je nach der Art der Fetts/iure beobachtet man die beschriebenen Erscheinungen bei verschie- denen Konzentrationen und Temperaturen. Beim Studium dieser elemen- taren Ph/inomene innerhalb der komplizierten Zusammensetzungen der Rasiercreme erwies sich die beschriebene Methode der Konsistenzmessung als /iuBerst niitzlich. iReceived : $Oth September 19581 LITERATURANGABEN Guest, H. H. in Sagarin, E. Cosmetics (1957). 422. (Interscience Publishers, Inc., New York and London.) Dayton, O. Journal ztmerican Oil Chemists Society, 30 (1953), 100. Zsigmondy, R., & Bachmann, W. Kolloid-Z., 11 (1912), 152. Bonadeo, I. Chem. Zentr. (1954), 2077. THE BEHAVIOUR OF COSMETIC CREAMS, LOTIONS AND OILS ON THE SKIN O. JACOBI, Ph.D.* Delivered at the Bonn Congress of the Gesellschaft Deutscher Kosmetik-Chemiker on 13th September 1958. The determination o• the spreading e•ect o• twenty different •atty and oily materials on the skin surface is described. The results show that the spreading and creeping o• these substances over the skin is o•ten quite extensive and is e•ected by viscosity and surface tension o• the •atty materials as well as by moisture content, the presence o• surface active X-materials o• the hornlayer and the sebum content o• the stratum corneum. The main cause is indicated as the capilarity o• the microstructure o• the skin's horny layer. THE QUESTION of percutaneous penetration of fats and oils incorporated in cosmetic products is always of big concern to the cosmetic chemist. In most cases the penetration of the total cream, lotion or oil is expected. * Kolmar Research Center, N[ilwaukee, Wise., U.S.A.

44 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS We know to-day that a percutaneous absorption in general means an absorption beyond the horny layer and there are two ways in which this can occur. One way is the transepidermal penetration, the other the absorption through the appendages of the skin. Rothman • recently described the mechanism of percutaneous penetration. There is evidence that certain electrolytes, lipid-soluble substances, gases, phenolic compounds, estrogenic hormones and lipid-soluble vitamins do penetrate the skin. There is, how- ever, very little or practically no evidence of the absorption of fatty sub- stances beyond the stratum corneum. Unna and his school 2 have shown in histological tests that lanolin and other ointment bases do not penetrate into the skin beyond the barrier. More recently Butcher a has confirmed this older result for lanolin using a different microtechnique. When Bernhardt and Strauch • applied different fats to the skin they were unable to demonstrate the absorption of any appreciable amounts. Barail and Pescatore 5 using a radioisotope technique were unable to show the penetration of U.S.P. cold cream into the skin. Lassa, v. Sobieranski and Sutton 6 and more recently Eller and Wolff 7 did, however, prove that animal, vegetable and mineral fats and oils enter the sebaceous glands. But according to Rothman 8 the amounts which penetrate into the follicles and are imbibed by the horny layer must be very small. This raises the question as to what happens to a cream, lotion or oil after rubbing into the skin if it does not penetrate. Czetsch-Lindenwald • describes what happens to creams and oils after their application to the hands. By incorporating a fluorescent dye in his experimental creams, lotions and oils he was able to demonstrate with a dark UV-light what happened to the products. They were transferred from the skin to instru- ments, tools, clothes, furniture, food and anything else that was touched with the hands. But this happens probably only to the excess. Where does the rest go ? A small part of it is absorbed by the horny layer and the follicles as mentioned above. The remainder spreads and creeps along the skin to areas which had not been treated. To study this problem we meas- ured the spreading and creeping of several cosmetic raw materials on the living human skin. We determined the spreading effect of twenty different fats and oils on a total of eleven healthy male and female subjects ranging between sixteen and sixty-eight years of age. Each substance was tested on four different skin areas. The skin areas were: the chest the inside of the upper arm near the shoulder close to the chest the forehead and the inside of the lower arm. The spreading was observed with a toplight skin microscope at a magnifica- tion of about 32 times. In addition a dark-ultraviolet lamp was also used. To be able to see the spreading of the materials under the dark UV-light,