TAURINE/ALOE VERA FOR BOOSTING ANTI-SKIN IRRITATION EFFECTS 225 prototype antiperspirant product containing 0.1% taurine and 0.1% aloe extract was found to signifi cantly reduce the production of IL-1α and IL-8 compared with con- trols in EpiDerm tissue (Figures 5 and 6). IL-8 is a chemokine that exerts chemotactic effects on neutrophils and lymphocytes. Increased expression of IL-8 by keratinocytes is a non-specifi c response to tissue damage due to chemical or physical agents (22). A human clinical study was conducted to assess the irritancy potential of our prototype product, and the results demonstrated that our prototype product signifi cantly reduced the pro- duction of IL-1α compared with a benchmark product (Figure 8). A commercial 12% AlCl3 antiperspirant product was used as a control and benchmark for our irritation ex- periments. These results demonstrated the applicability of taurine and aloe extract in reducing skin irritation to dermatological vehicles. Data obtained from SEC revealed that the additional of taurine and aloe extract into formulation did not alter the size distribu- tion of Al3+. This suggests these anti-irritating agents do not affect the polymerization of AlCl3, which suggests the sweat reduction effi cacy would remain intact (Figure 1). From our studies, we were able to develop an effi cacious, antiperspirant formulation with re- duced irritation potential. Finally, we sought to understand the mechanism of the boosted anti-irritating effect of the taurine and aloe extract blend. Taurine has two largely separated pKa, a very low pK1 (1.5) from the sulfonic acid group and a high pK2 (9.08) from the amino group which give rise to a zwitterion over a wide pH range. Under our experimental pH range Figure 7. EpiDerm tissue was lysed at set time points and intracellular taurine concentration was measured using HPLC. Tissues were treated with either PBS solution containing only taurine or PBS solution with both taurine and aloe extract to assess the permeation enhancing effects of aloe extract on keratinocytes.

JOURNAL OF COSMETIC SCIENCE 226 (2.5 pH 4), taurine exists as the zwitterionic form with high water solubility (104.8 g/l) (Figure 9) (12). Compared with the cationic and anionic forms, the zwitterionic form readily pene- trates the skin barrier into keratinocytes (8). Previous research has disclosed that tau- rine is predominantly localized to the stratum granulosum and stratum spinosum in the epidermis (12). Aloe vera extract has been previously found to enhance the trans- port of various drugs and compounds across skin and intestinal epithelial cells (23). There are several hypotheses as to how aloe vera enhances the permeation of certain compounds. Figure 9. Speciation of tau rine under varying pH concentrations is shown. The zwitterionic form is the most predominant form at biological pH values. Figure 8. Subjects (n = 1 2) were treated with a commercial 12% AlCl3 antiperspirant benchmark product and a prototype 12% AlCl3 product containing 0.1% taurine and 0.1% aloe extract (one on each designated forearm area). IL-1α concentration was measured after four consecutive days of dermal exposure from obtained skin samples. *p 0.05.