by Robert J. Friedman, M.D., M.Sc. (Med.), Clinical Professor, NYU School of Medicine, Chairman and Founder, MDSolarSciencesTM
Almost all of us are used to thinking about sun protection by the numbers. SPF, or sun protection factor, has long been considered the only thing that matters. The common perception is that a higher number equals more protection. While true, it really only tells half the story. A higher SPF number means greater protection from one kind (UVB) of ultraviolet (UV) light given off by the sun. In order to understand the true nature of sun protection, we have to understand the two types of UV light and how they damage your skin.
Ultraviolet B (UVB) radiation is the main cause of sunburn. UVB rays do their damage right at the point of impact: the top layer of skin. The intensity varies throughout the year, ramping up in the summer months (and peaking every day at noon), right as we all want to be out in the sun. Another thing that affects UVB intensity is altitude. UVB intensity increases 5% every 1,000 feet. UVB rays do not penetrate your car or office window, which is why you don’t get burned on those long road trips. Protecting yourself from sunburn is important, but it can also lead to a false sense of security. There is another threat to your skin that requires year-round protection.
Ultraviolet A (UVA) rays make up 95% of the UV radiation that reaches Earth. The longer wavelengths make them less intense than those of UVB, but there are 30 to 50 times more UVA rays at any given time. UVA rays are longer than UVB, allowing for deeper skin penetration, which causes wrinkling, discoloration, and aging. Because there is no painful, immediate consequence of UVA exposure (like the sunburn caused by UVB), too many people take an “out of sight, out of mind” attitude to UVA protection. Just because you can’t see the damage being done, don’t think that you aren’t being exposed. Unlike UVB, UVA rays are consistent throughout the year (and throughout the day). UVA rays can also pass through clouds and glass, meaning that car or even airplane windows can’t help you. Both UVA and UVB rays contribute to skin cancer. So how do you make sure you’re fully covered?
Simply put, a broad spectrum sunscreen provides protection against both UVA and UVB rays. It covers the full spectrum of UV radiation, giving you complete protective coverage. So what about those SPF numbers that have long been the one and only thing that people care about? While important, SPF only deals with UVB rays. The SPF numbers tell you how long it will take for UVB rays to burn your skin with the product versus without the product. SPF has absolutely nothing to do with UVA rays. In order to be fully protected from the sun’s harmful rays, a product needs to cover the entire UV spectrum. It needs to have active ingredients working together to protect you from UVA and UVB radiation. In other words… if it doesn’t say broad spectrum on the label, you’re basically wasting your time. That’s why all MDSolarSciencesTM sunscreen products are formulated to provide safer broad spectrum protection, no matter the SPF. Our Sun Care formulas may have different SPF levels, but check the labels and you’ll find one important commonality – they are all broad spectrum.