200 JOURNAL OF COSMETIC SCIENCE formulation after tape stripping, solvent treatment, and some types of detergent treat­ ment (102). Specifically, topical application of the physiologic lipids cholesterol, cer­ amide, palmi tate, and linoleate in the ration of 4. 3: 2. 3: 1: 1. 08 showed enhanced barrier recovery. However, it must be noted that in barrier repair-vs-hydration studies, corre­ lations between the moisturizing properties and barrier repair mechanism of applied lipid mixtures are not always evident. Actually, the best hydrating lipid composition is often different from the optimal barrier repair formulation and vice versa (101). FROM OLD TO NEW CONCEPTS Classical vehicles in dermatology are amphiphilic systems (60). An example is given from the German pharmacopoia: Base cream DAC Glycerol monostearate 60 Cetyl alcohol Mid-chain triglycerides White petrolatum Macrogol-1000-gl ycerol monostearate Propylene glycol Purified water 4.0 6.0 7.5 25.5 7.0 10.0 40.0 The problem with these formulations is the high content of emulsifiers that might have a negative effect on long-term application or counteract the positive features of the vehicles. A new approach is the use of hydrogenated polydecenes. They are special oligomers of decene, with branched isoparaffinic structures completely saturated after full hydroge­ nation. It has been shown that they are soluble in most nonpolar solvents and can be blended with common lipids. They spread easily, do not interfere negatively with the skin barrier, and are not occlusive (77). An example of a cream is given as follows: Allantoin Trimethylglycine Panthenol Carbomer Hydrogenated polydecene (NB 2004 FG)4 Limnanthes alba + butyrospermum parkii PPG-15 stearyl ether (a) Steareth-2 (b) Steareth-21 (c) Preservatives Tocopheryl acetate Sodium hydroxide Actives Purified water 4 Fortum Oil and Gas Oy, Base Oils, P.O. Box 100, 00048 Fortum, Finland. 0.10 1.00 0.20 0.50 6.50 2.50 1.00 2.00 1.00 q.s. 0.50 0.2 q.s. ad 100.00

ROLES OF VEHICLES FOR SKIN TREATMENT 201 Hydrogenated poyldecenes might replace mineral oils in vehicles. This formula is very versatile, as all types of lipid ingredients (e.g., polyunsaturated), except silicones and water-soluble molecules, can be added. Very high lipid content can be reached by simply increasing the amount of emulsifiers (a,b,c). In spite of their low polarity, polydecenes are good solvents for most liposoluble active principles (e.g., retinoic acid). They can be dissolved in the oily-plus-emulsifiers phase before the addition of the aqueous phase. Polydecenes show moisturizing properties higher than mineral oils. CONCLUSIONS In this review, different roles of vehicles for skin treatment have been presented, in­ cluding cosmetic vehicle classification, with some examples of compounded vehicles and the effects of vehicles, with specific focus on barrier protection and barrier recovery. An extended discussion has been presented on the special functions of lanolin, petrolatum, and physiological lipids in cosmetic vehicle formulation. Choosing the appropriate cosmetic vehicle for the treatment of different skin diseases may have a high impact on the clinical outcome of a treatment and even more on the relapse-free period. The chosen cosmetic vehicle should no longer be regarded simply as a drug carrier or vehicle or as a drug delivery system, but as an essential part of topical treatment. Optimal lipid ratios within the vehicle have been shown to be therapeutically beneficial in patients with atopic dermatitis. Thus, it may be of importance to adapt type and composition of the cosmetic vehicle according to the evolution of the disease, either as an adjuvant treat­ ment or as a drug delivery system, especially in dermatological prescriptions. This review is intended to provide a better understanding of the specific functions of der­ matological and cosmetic vehicles and to enable an evidence-based use of different vehicle types with specific compositions. REFERENCES (1) M. Gloor, K. Thoma, et al., Dermatologische Externatherapie (Springer-Verlag, Berlin, Heidelberg, New York, 2000). (2) K. De Paepe, J. P. Hachem, et al., Beneficial effects of a skin tolerance-tested moisturizing cream on the barrier function in experimentally-elicited irritant and allergic contact dermatitis, Contact Der­ matitis, 44, 337-343 (2001). (3) S. L. Chamlin, J. Kao, et al. Ceramide-dominant barrier repair lipids alleviate childhood atopic dermatitis: Changes in barrier function provide a sensitive indicator of disease activity,]. Am. Acad. Dermatol., 47, 198-208 (2002). (4) C. Billmann-Eberwein, F. Rippke, et al., Modulation of atopy patch test reactions by topical treat­ ment of human skin with a fatty acid-rich emollient, Skin Pharmacol. Appl. Skin Physiol., 15, 100-104 (2002). (5) L. Lehmann, M. Gloor, et al., Stabilitat und Okklusivitat von Externagrundlagen auf der Haut, Z. Hautkr., 872, 585-590 (1997). (6) C. W. Blichmann, J. Setup, et al., Effects of single application of a moisturizer: Evaporation of emulsion water, skin surface temperature, electrical conductance, electrical capacitance, and skin surface (emulsion) lipids, Acta Derm. Venereal., 69, 327-330 (1989). (7) M. Loden, The increase in skin hydration after application of emollients with different amounts of lipids, Acta Derm. Venereal., 72, 327-330 (1992). (8) J. W. Fluhr, G. Vrzak, et al., Hydratisierender und die Steriodpenetration modifizierender Effekt von Harnstoff und Glycerin in Abhangigkeit von der verwendeten Grundlage, Z. Hautkr., 73, 210-214 (1997).