442 Improvement a Improvement b � 4.5 ·;:: ·5 4 'j 3.5 JOURNAL OF COSMETIC SCIENCE 0 --.--------------------------, -4+----�---------�--------1 Baseline Day 1 Day 1 Week 1 Evaluation Week 1 Evaluation Week2 Week2 -•-- Regimen GR -- ,. -- Regimen LG -Regimen GR - • - Regimen LG Figure 5. Results of the home-use validation study. The effects of different regimens on panelists' skin conditions were assessed in a home-use study. The panelists' skin was evaluated by (a) a dermatologist and (b) the panelists. alternative mechanism that has been demonstrated in vivo is the stimulation of the enzymes that are responsible for proper desquamation (25). Another possibility proposed by Froebe, Mattai, and their colleagues (26,27) from in vitro studies is that glycerin can prevent the phase transition of stratum cornuem lipids from liquid crystal to gel phase even when the bilayer is partially dehydrated. This phase change in the lipid bilayer can result in an increase in water loss, and in vivo this may affect the stratum cornuem water barrier. These studies suggest that glycerin can work by a variety of different mecha­ nisms. However, for many of these mechanisms to be realized, glycerin must be able to penetrate into the stratum cornuem. This does occur, with glycerin being delivered to

MOISTURIZER EFFICACY 443 the epidermis at a rate of tens to hundreds of micrograms of glycerin/cm2 from the test lotions LG and GR, respectfully, after 24 hours (data not shown). Recently, glycerin has been demonstrated to be able to reduce irritation potential. Fluhr et al. (28) showed that glycerin accelerated the repair of the stratum cornuem barrier of human volunteers when tape stripping had disrupted the barrier. The recovery, com­ pared with that of damaged but untreated skin, became significantly greater after three days and occurred whether the glycerin was applied openly or occluded to the damaged skin. Occlusion alone did not enhance recovery. Similar damage to skin was observed when washing with aqueous SLS solution, except that recovery appeared to take longer. However, the mechanism by which glycerin reduces irritation is not well understood. Mauro et al. (29) showed that barrier-function repair in mice occurs more rapidly at pH 5.5 than at 7.4. They speculated that the repair process involves extracellular lipid­ processing enzymes, whose pH optima is somewhat acidic. It should be noted that the pH of lotion GR (at 4.5) was the lowest (most acidic) of the lotions tested. Ultimately, it is important to demonstrate the relevance of controlled laboratory meth­ ods, whether in vivo or in vitro, to our consumers. This is the reason for running the home-use validation study. By using a group of consumers with a low level of derma­ tological distress (perceived itching, but few other clinical signs of eczema), we were able to show that a regimen based on using a high-glycerin lotion (GR) was significantly more effective than a regimen based on a low-glycerin lotion for both subjective and observable signs of eczema. This validates the predictions of the controlled in vivo studies. REFERENCES (1) D.R. Highley, V. 0. Savoyka, J. J. O'Neill, et al., A stereomicroscopic method for the determination of moisturizing efficacy in humans,]. Soc. Cosnzet. Chem., 27, 351-363 (1976). (2) G. L. Grove, Skin surface hydration changes during a mini regression test as measured in vivo by electrical conductivity, Curr. Ther. Res., 52, 556-561 (1992). (3) M. Loden and A.-C. Andersson, Effect of topically applied lipids on surfactant-irritated skin, Br. J. Derrnatol., 134, 215-220 (1996). (4) A. Hannuksela and T. Kinnunen, Moisturizers prevent irritant dermatitis, Acta Derin. Venereal. (Stockh.), 72, 42-44 (1992). (5) H. Zhai, F. Brachman, A. Pelosi, et al., A bioengineering study on the efficacy of a skin protectant lotion in preventing SLS-induced dermatitis, Skin Res. Technol., 6, 77-80 (2000). (6) A. M. Kligman, Regression method for assessing the efficacy of moisturizers, Cosmet. Toiletr. 93, 27-35 (1978). (7) E. K. Boisits, G. E. Nole, and M. C. Cheney, The refined regression method,]. Cutan. Aging Cosmet. Dermatol., 1, 155-163 (1989). (8) H. Zhai and H. I. Maibach, Moisturizers in preventing irritant contact dermatitis: An overview, Contact Dermatitis, 38, 241-244 (1998). (9) C. E. Gammal, A. Fagnoni, A. M. Kligman, et al., A model to assess the efficacy of moisturizers-The quantification of soap-induced xerosis by image analysis of adhesive-coated discs (D-Squames), Clin. Exp. Dernzatol., 21, 338-343 (1996). (10) P. J. Frosch and A. M. Kligman. The soap chamber test: A new method of assessing the irritancy of soaps. J. Am. Acad. Dermatol. 1, 35-41 (1979). (11) H. Schatz, A. M. Kligman, S. Manning, et al., Quantification of dry (xerotic) skin by image analysis of scales removed by adhesive discs (D-Squames),j. Soc. Cosmet. Chern., 44, 53 (1993). (12) L. M. Wall and K. A. Gebauer. Occupational skin disease in Western Australia, Contact Dermatitis, 24, 101-109 (1991).