THE GREASINESS OF MOISTURIZERS 179 Table II Coefficients of Variation for Different Variables Parameter studied Changes Coefficient of variation (%) Volume of moisturizer 25 pl/25 cm 2 35 50 pl/25 cm 2 14 100 pl/25 cm 2 23 150 pl/25 cm • 8 Area 25 cm 2 14 100 cm • 22 Post-application time 20 rain 23 40 rain 18 60 rain 12 120 min 34 180 rain 44 Blotting time 30 s 31 45 s 11 60 s 21 90 s 12 120 s 8 Load on blotting Rubber-gloved hand 17 1 kg 17 Anatomical region Volar forearm 13 Back 11 Blotting paper OOH (small pores) 20 OOK (medium pores) 18 OOR (large pores) 20 BB (standard, mixed-size pores) 20 Previous studies have used the Sebumeter for the assessment of skin surface lipids (1). Actual use of moisturizers or other creams, however, involves the application of amounts of lipids that are in excess of the range of the optic method, and Sebumeter measure- ments were therefore performed after blotting. Blotting is modified by many factors, including the film-forming capacity of the lipids and the steady state achieved by the diffusion of lipids in and out of the superficial compartment of the skin. Using the Sebumeter for further measurement of skin surface lipids after blotting therefore adds validity to the proposed method. A significant correlation between the two methods was seen (rs -- 0.53), although considerable scatter was noted on single measurements, suggesting the two methods give mutually supportive rather than mutually exclusive results and should perhaps be used together. Using the proposed method to compare the greasiness of commonly used moisturizers, protective creme, and gel also showed that the results appear to be in good accordance with the general clinical impression, al- though a panel of test persons were not used in this study. Of the moisturizers examined, Vaseline © and Locobase © leave the most residue, while gel and the cosmetic moisturizer from Clinique © leave the least residue. The dry or lipid content of each moisturizer is, of course, a key factor. Vaseline © has a very high dry content, while moisturizers developed primarily for cosmetic use and gels have a high water content. This would aj r•ori suggest that the latter products exert their

180 JOURNAL OF COSMETIC SCIENCE 300 250 200 150 100 50 -5O , I lO 20 rng blotted Figure 1. Correlation between the amount of moisturizer blotted and the post-blotting skin surface lipid as measured by the Sebumeter (R 2 = 0.5272). effect mainly through direct hydradon of the skin, while the greasier products act through lipidization. The previous notion of an occlusive effect has not been substan- tiated (2). The proposed simple method makes practical testing of greasiness possible. Many factors are involved in this practical quality of moisturizers, and it has been proposed that differences in emolliency may partly be predicted by the emollients used. Brand and Brand-Garnys have suggested emolliency to be a function of the inherent spreadability and lubricity of moisturizer constituents (4). These qualities can be pre- determined for a reduced development time of actual products, and the final results can potentially be verified by our proposed method. The exact formulation is, however, also of obvious importance, and, for example, the use of liposomes may increase absorption as reflected by the lower amount of unabsorbed residue in the Nivea © moisturizer. The efficacy of moisturizers is of immediate practical interest, and it is speculated that the effects vary according to the absorption of either the water or lipid phase. A previous study has suggested that the water phase evaporates within the first 15 minutes of application and that longer-term effects, i.e., after ten minutes or more, are therefore more likely to be due to absorption of the lipid phase (1). The protective cream studied (Kerodex ©) showed a picture dissimilar from that of the moisturizers. This cream is designed to leave an adherent and water-protective layer on the skin surface (2). In clinical use there is an impression of occlusive "residue," but our investigation shows that actual greasiness is very low, as would be required for any practical use of a protective cream. Practical use of moisturizers suggests that a considerable residue of excess unabsorbed moisturizer is left on the surface of the skin to be absorbed by the clothes or worn off at no benefit to the user. This unabsorbed excess is greasy and may affect frequency of use and general cosmetic acceptability of any given moisturizer. Quantification of this unabsorbed moisturizer therefore offers quantitative and clinically relevant data on the