Prevention of Skin Cancer: Healthy Sun Exposure and No sunscreen for Intense Intermittent Exposure; Photoaging Theories Questioned and New Strategies

Abstract

Currently the FDA adopts a zero-tolerance policy toward sun exposure in order to prevent skin cancer and premature skin aging (photoaging). This is apparently based on classical concept that damage from sunlight, a carcinogen, is cumulative and un-reparable. Such concept is apparently flawed both theoretically and in reality. The nature’s design to achieve genomic stability of body health and appearance for smooth passage of generations in our normal daily lives would require virtually complete repair of damages of DNA and other tissue components from daily Exposure to Non-Burning Sunlight (ENS). In other words, ENS is generally not expected to cause skin cancer and photoaging. Such notion is evidenced by, for example, low worldwide skin-cancer incidences, severe sunburn as overwhelming skin-cancer etiology, and intrinsic aging as overwhelming skin aging. Since ENS can provide numerous health benefits, such exposure can be regarded as healthy sun exposure and used to help prevent skin cancer. Due to unintended sunburn effect, use of sunscreens for intense intermittent exposure is strongly discouraged. As photoaging and skin cancer may be closely related, some questions related to conventional theories and practices in photoaging are also raised. They include the following: Schuster’s pioneering study in 1975; invalidation of accelerated aging theory; questionable theory on etiology of wrinkles and age spots; Fisher’s studies on metalloproteinases; bolus doing vs constant-rate dosing in irradiation; moisturizers as anti-photoaging/anti-cancer agents; inclusion of blood and water in skin-aging exosome; wind effect; differences in usage pattern between countries in sunscreen evaluation; replacement of UVA in tanning beds.