Abstract:
Two of the most frequently used sunscreens, benzophenone-3 and octyl p-methoxycinnamate, were formulated into hydroalcoholic, diisopropyl adipate oil prototype formulations and oil-in-water (o/w) and water-in-oil (w/o) emulsions. Various polymers at 5% wt./wt. were included in these formulations. We developed an in vitro procedure for measuring the water resistance of sunscreens and assessing their ability to resist wash-off. Results of our in vitro procedure were comparable to in vivo findings reported in the literature. With tricontene-PVP copolymer present in the o/w emulsion, a statistically significant increase in retention of benzophenone-3 by stratum corneum was obsd.