34 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ment (Figure 1C) is able to partially reform the lameliar lipid-like structure whereas the petrolatum-cholesterol-stearic acid treatment cannot (Figure 1D). Thus, it is apparent that the phospholipid-based lipid system, because of its bilayer-forming properties, may offer a potential advantage over the non-bilayer-forming petrolatum-based lipid system if such combinations are incorporated into moisturizers. IN VIVO STUDIES It is first noted that the respective treatment effects for the negative control (no treat- ment) as well as for the positive control (standard commercial moisturizer) did not differ significantly from study to study. This allowed for valid statistical comparisons of the different product treatments using absolute dryness scores irrespective of the study group a particular treatment was used in. Figures 2 and 3 show that 1% glycerol (treatment 1) and 4% phospholipid-cholesterol- stearic acid mixture (treatment 2) alone are ineffective in alleviating skin xerosis com- pared to the no-treatment control over this particular time course. However, as seen in Figure 4, the results for the combined treatment (treatment 3:4% phospholipid- cholesterol-stearic acid, plus 1% glycerol) show a marked improvement in skin xerosis 7 "'6 ill Treatment phase Regression phase 0 5 10 15 20 DAYS Treatment 1 No Treatment Figure 2. Moisturization efficacy test comparing the effect of 1% glycerol (treatment 1) to a no-treatment control.

EFFECT OF LIPIDS ON SKIN XEROSIS 35 7 "'6 Regression Treatrner•t phase 1 ' , i • i phase • 0 5 10 15 20 DAYS Treatment 2 No Treatment Figure 3. moisturization efficacy test comparing the effect of a lotion containing 1% phospholipid, 2% cholesterol, and 1% stearic acid (treatment 2) to a no-treatment control. alleviation in contrast to those for the two individual treatments shown in Figures 2 and 3. Figure 5 shows the effectiveness of 5% glycerol combined with 4% of either of two different ternary lipid mixtures. It can be seen that when phospholipid is used in the lipid mixture instead of an equivalent amount of petrolatum (treatment 4: phospholipid- cholesterol-stearic acid, plus 5 % glycerol, vs treatment 5: petrølatum-chølesterøl-stearic acid plus 5% glycerol), a more rapid response (p 0.05 by Day 8) in skin xerosis alleviation is observed, although both treatments were effective in alleviating dry skin over the larger time frame of the study. DISCUSSION Occlusive agents and humectants have been used widely in skin care products for the treatment of skin xerosis over many years. Because of a lack of understanding of the pathophysiology of skin xerosis, improvements in skin care treatments have been em- pirical. Recently, however, several investigators have reported specific abnormalities in stratum corneum structure and composition in winter xerosis (13-15). These studies have shown that skin xerosis is related to changes in stratum corneum ceramide levels and a disturbance in their structure, as well as to an abnormality in desmosome pro-