ASSESSMENT OF HYDRATION EFFECT OF A COSMETIC TREATMENT

Lorelai I. Ciortea1, Robert E. Imhof2, Flavius C. Pascut2

1INCDTIM, P.O.Box 700, RO-400293 Cluj-Napoca 5, Romania
2London South Bank University, London, UK

Introduction: The aim of these experiments was to evaluate the hydration effect of a cosmetic treatment on ten volunteers in a controlled clinical study.
Matherials and Methods: F-OTTER (Fibre-Optothermal Transient Emission Radiometry) and Corneometer were used to measure SC moisture content, whereas TEWL (TransEpidermal Water Loss) was used to measure water vapor flux coming from the skin [1,2,3]. The measurements were performed alongside each others, in order to study the relationship between water content and evaporative flux. In the experiments reported here, measurements were performed after treating the left and right volar of the volunteers forearms in a randomized way, with two different _oisturizing creams provided by a Cosmetic Company. Before measurements, volunteers were acclimatised for 15 minutes in an air-conditioned room with the forearms exposed to the ambient conditions (=20°1°C, RH=40% 1%). A grid of 5 measurement sites on each forearm was marked out from wrist to elbow, followed by the application of 2mg/cm2 of the two creams respectively to the left and the right forearms. Measurements were taken on each site before applying the products and at the following times respectively: 0 hour for Site1, 1 hour for Site2, 2 hours for Site3, 4 hours for Site4 and 6 hours for Site5 after cream application. The cream was gently wiped off before each measurement. 
Results and Discussion: The results given by F-OTTER revealed a decrease in hydration after cream application, while the results given by Corneometer showed an increase of hydration after cream application. These results appear to be contradictory, but the explanation could come from the penetration depths of the measurement 10µm for F-OTTER and 30-40 µm for Corneometer. The indicated decrease in hydration given by F-OTTER could be due to 1) cream diffusion through the SC and 2) replacement of water molecules in the SC with cream molecules. There is some support for the first mechanism by the TEWL results, which showed a decrease of flux density after cream application; the second mechanism is suggested by the lower values of hydration after cream application as given by F-OTTER. The increase of hydration index given by Corneometer could be explained by a better contact between the skin and the probe, as the cream application causes the skin to become smoother.
Conclusions: Although the action of the hydrating creams is considered only in the SC, from the results presented it seems that reconsiderations should have be taken regarding their depth of action. 

References:
1. R.E. Imhof, Method and equipment for measuring vapour flux from surfaces. UK Patent Application No. 9814862.0, 1998.
2. R.E. Imhof, D.J.S Birch, F.R. Thornley, J.R. Gilchrist and T.A. Strivens, Optothermal Transient Emission Radiometry, J. Phys. E: Sci. Instrum., 17:521-525, 1984. 
3. CK Electronics, http://www.courage-khazaka.de