About the Author Antony R. Young, Emeritus Professor of Experimental Photobiology . Professor Young’s research career has focused on the effects of sunlight on human health, which are benefi cial as well as detrimental. Thus, it is important to understand the balance between the pros and cons of solar exposure, which vary with different Fitzpatrick skin types. An important part of this work has been on photoprotection by sun- screens and pigmentation. Most photobiology research has been done under laboratory conditions, often with solar simulated radiation, mainly because these are relatively easy to control. However, there is an increasing awareness that the laboratory does not necessarily predict what happens in the fi eld, and this is especially true with sunscreens. In recent years, Prof. Young has been engaged with “holiday studies” to deter- mine the effects of real sun on photobiological outcomes, including the effects of sunscreens. Prof. Young has been a regular contributor to meetings of the American and European Societies for Photobiology, as well as dermatology congresses. He is also a member of the United Nations En- vironment Programme (UNEP)—Environmental Effects Assessment Panel.
J. Cosmet. Sci., 71, 217–225 (July/August 2020) 217 Comparison of Skin Photoprotection by Pigmentation and Sunscreens ANTONY R. YOUNG , St John’s Institute of Dermatology, King’s College London, London, United Kingdom (A.R.Y.) Synopsis Melanin, in people with naturally pigmented skins, offers a high level of photoprotection against the adverse molecular and clinical effects of solar ultraviolet radiation but, in contrast, has a modest inhibitory effect on vitamin D synthesis. Tanning in those with light skin offers relatively modest photoprotection. Sunscreens have the potential to offer high levels of protection in people who lack melanin. In theory, sunscreens can give protection comparable with that of deeply pigmented skin. This depends on the labeled sun protection factor (SPF) which in turn depends on how well the sunscreen is applied. In most cases, this will not achieve the desired SPF. The threshold dose for vitamin D synthesis is much lower than that for sunburn, such that vitamin D synthesis is still possible with sunscreen application. INTRODUCTION The adverse clinical effects of solar ultraviolet radiation (UVR ~ 295–400 nm) on human skin are well documented. Solar range UVR also has effects on the skin (1) and blood (2,3) transcriptomes. The only fully established benefi t is vitamin D syn- thesis by UVB (280–315 nm) that is much more important than vitamin D intake from food sources. There is, however, increasing evidence of other benefi ts from solar exposure, such as a reduction in blood pressure (4). Cutaneous responses to sunlight are highly dependent on the Fitzpatrick skin type (FST) that ranges from I (very light) to VI (very dark) thus, FST I is much more prone to sunburn (erythema) and skin cancer than FST VI. The most probable reason for this is the amount of melanin in the epidermis. In other words, melanin is a very effective natural sunscreen. The presence of melanin is either constitutive or facultative the former being the natural baseline level present in habitually sun-protected skin (i.e., buttock), whereas the latter is tanning in response to solar or other UVR exposure. Facultative pigmentation is also FST dependent. Most photobiological research on human skin in vivo has been carried out on lighter FSTs ranging from I (e.g., Celtic) to IV (e.g., Mediterranean). Relatively little has been carried out on FST V (e.g., Indian subcontinent) and VI (e.g., African) (5). The most widely used Address all correspondence to email@example.com
Purchased for the exclusive use of nofirst nolast (unknown) From: SCC Media Library & Resource Center (library.scconline.org)