Healthy skin possesses an antioxidant defense system against oxidative stress. However, overexposure to ultraviolet radiation (UVR) can overwhelm this defense system’s capacity, leading to skin disorders such as sunburn, photosensitivity reactions or immunologic suppression, as well as photoaging, malignant skin tumors and other long-term sequelae. Application of topically exogenous antioxidants may prevent or minimize such damage.
A previous column by these authors described a rapid, accurate and facile method to quantify the antioxidative capacity of topical formulations in vitro. The present article introduces an in vivo model using a photochemiluminescence device and biophysical methods to determine the antioxidative capacity of a topical o/w skin care emulsion with and without vitamin E. The human skin tested was exposed to UVR.
Materials and Methods
Subjects: Ten healthy Caucasians (three male and seven female; mean age 47 ± 10) of the skin types II or III were enrolled. The Committee on Human Research at the University of California, San Francisco approved this study.
Test materials: A facial skin care o/w emulsion was obtained with pH balanced at 5.5% and 22.5% oil content. The emulsion contained water, petrolatum, myreth-3 myristate, glycerin, cetearyl alcohol, tocopheryl acetate, ceteareth-20, dimethicone, sodium PCA, sodium citrate, sodium carbomer, fragrance, benzyl alcohol, methylparaben and propylparaben. The active ingredient in the test emulsion was 2.3% vitamin E as tocopheryl acetate; the vehicle control contained no vitamin E but was otherwise identical. Study design: The study was randomized, double blind and placebo-controlled.