ABSTRACT
Repeated long-term exposure to ultraviolet radiation causes skin aging and increased risk of skin cancer, whereas acute exposure can cause sunburn and significant discomfort. Strategies that have been demonstrated to protect the skin, including the regular use of efficient sunscreens, are heavily promoted by cancer prevention organizations and can provide better health outcomes for individuals and cost savings for health care systems. Consequently, sunscreen actives are present in many cosmetic and personal care products, as well as “beach sunscreen” products. In all cases the advice is to apply liberally, well before expected sun exposure. Sunscreens are used to protect against solar ultraviolet radiation. Sunscreen products are typically formulated to provide high skin substantivity. It is therefore important that in vitro experiments are designed to assess both permeation through the skin and penetration into/retention in the skin over the time course of topical application.
