GLYCOLIC ACID IN W/0/W EMULSION 491 Table IV Data of Particle Size Analysis (µm) by Microscope Method Days 4°c 25°c 31 ° c Formulations PD 30 60 90 30 60 90 30 60 90 G 9.025 7.976 7.413 6.095 7.019 6.477 5.066 6.664 5.480 4.966 GD 10.182 9.701 8.766 6.658 6.590 6.560 5.290 6.769 6.556 6.505 GS 8.078 7.058 5.673 5.274 6.899 GDS 10.710 9.688 8.225 5.636 8.210 7.660 6.378 6.919 5.938 5.135 PD: production date. Table V Viscosity Values of the Formulations at 25°C Days PD 7 30 60 90 Viscosity SD Viscosity SD Viscosity SD Viscosity SD Viscosity SD Formulations (cp) (±) (cp) (±) (cp) (±) (cp) (±) (cp) (±) F-G 40467 385 30500 509 21800 355 20933 478 18500 216 F-GD 43933 997 33967 1483 28867 612 26567 498 20567 498 F-GS 16000 216 12933 124 F-GDS 19200 163 16433 124 12133 612 14133 834 10900 294 PD: production date. days, respectively. The viscosity of F-GDS was 19200 cp at the production date and was found to be 1413 3 cp and 10900 cp after 60 and 90 days, respectively, at 2 5 °C. This much decrease in viscosity doesn't affect stability, which is also confirmed by organo­ leptic controls and microscopic and particle size analyses. Multiple emulsions containing GA, GA and D, GA and S, and GA, D and S were investigated and compared on ten volunteers' inner arms by using panel tests to examine chemical peeling and its side effects. The purpose of this study was to evaluate whether GA improves skin barrier function when preventing skin irritation by strontium nitrate. Skin care products are complex formulations that may cause sensory irritation symptoms, characterized by stinging, burning, and itching. Substances capable of counteracting sensory irritation are of great practical interest. Collagen hydrolysates are reported to be used for this purpose (24). Strontium salts have been demonstrated to inhibit sensory irritation and inflammation when applied topically. In our study, we evaluated the efficacy of strontium nitrate in reducing chemically induced skin sensory irritation in ten subjects. SKIN SENSORY TEST DESIGN Ten healthy subjects (aged 27 +/- 5 years) entered the study. The test site was the forearm of each subject. Each test site was 6 cm x 4 cm in size. Four different formu­ lations and an untreated control were applied to the test sites as in a similar referenced

492 JOURNAL OF COSMETIC SCIENCE study (25). The products were applied every day to the same sites for ten days straight. The actual amount of product applied to the test site each day was 2 g/cm2 . At the end of the study each panelist filled out a permission consent form and a questionnaire. The questionnaire asked the test subjects their opinions about the side effects caused by the formulations when used for chemical peeling. The irritation sensation was evaluated each minute for the first 20 minutes after topical application, using a scale from 0--4. The duration of the irritation sensation in minutes was also recorded. As can be seen from Figure 1, formulations G and GD showed the highest redness, itching, pain, and edema, respectively, when compared to GS and GDS, which contained strontium nitrate, while the peeling effects were a little higher in the cases of GS and GDS. GS in comparison with G alone, markedly (p 0.01) shortened the duration of the irritation sensation from 20.6 ± 3.8 min. to 7 .2 ± 2.6 min., and significantly (p 0.05) reduced the magnitude of the pain sensation at all time points. The study demonstrated that GS and GDS formulations suppressed the sensation of pain, edema, redness, and itching. CONCLUSIONS The current investigations have shown that the choice of preparation conditions for formulations, such as oil phase volume, temperature, mixing rate and time, the addition of electrolytes, the type of mixing shaft, and the densities of internal and external phases, play an important role in the stability of multiple emulsions, which is of prime impor­ tance. After long investigations, optimal conditions were chosen and stable multiple emulsions could be produced with all the ingredients involved in this study. In the second part of the study, after obtaining the stable multiple emulsions, panel tests were 10· 9 8 7 6 5- 4- 3 2- 1 a Effects of glycolic acid on skin Figure 1. Data of multiple emulsion formulations obtained from panel test. G (bar l) GD (bar 2) GS (bar3) GDS (bar 4).