INVITRO SUN PROTECTION FACTOR EVALUATION OF SUNSCREEN PRODUCTS

An in vitro method to evaluate sunscreen products for static sun prote ction factor (SPF) was investigated. Surgical adhesive tapes were used as substrates in a procedure modified from that originally described by Diffey and Robson, 1989. The modified technique utilized a 150-watt xenon arc solar simulator and an ultraviolet B radiometer. The in vit ro SPF was calculated as the ratio of light transmission through untre ated tape to that of sunscreen-treated tape and compared to SPFs deter mined in vivo. Correlation between in vivo and in vitro SPF data varie d tremendously. The sources of error were attributed to the structure of the tape, absorption of the sunscreen active ingredients into the t ape, and the detection limit of the radiometer used.