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Five Facts about Sunscreen You Never Knew

Spring upon us, and that means one thing: time to break out the sunscreen! Since UV light is responsible for over 80 percent of the signs of aging, sunscreen is the Holy Grail of anti-aging products. Yet, despite the fact that over $550 million worth of sunscreen is sold in the U.S. alone each year, almost no one seems to know all of the essentials about it. Here are five of the most little-known facts about every dermatologist’s favorite product:

1.) 1 Divided by the SPF = the Percent of Rays that Get Through
Unless a product is labeled as “Broad Spectrum,” SPF numbers only assess short-wavelength UVB protection, not long-wavelength UVA protection. UVB rays contribute most to sunburns and inflammation, so understanding how SPF numbers work is vital.

To figure out the level of protection in a sunscreen, divide 1 by the SPF number. That equals the percentage of rays that sneak past the product. For example, with SPF 25: 1/25 = 4 percent of rays pass through. With SPF 50, 1/50 = 2 percent of rays pass through. You may notice as you get higher, the percentage of benefit decreases—SPF 100 is only one percent more effective than SPF 50, but SPF 50 is 2 percent more effective than SPF 25. For this reason, the European Union does not allow sunscreen manufacturers to post that a sunscreen rating is higher than 50; instead, packaging there can only state a maximum of “50+.” I say go for the highest rating possible, but I do see the benefit of wanting to prevent consumers from being mislead.

2.) Zinc Oxide > Titanium Dioxide
The longer a ray’s wavelength, the more it contributes to aging. UVA rays are longer than UVB rays, so remember that UVA = aging, while UVB = burning. Among the UVA protectors, zinc oxide is the king, aszinc oxide absorbs more UV light than competitor titanium dioxide in the long-wave UVA spectrum.

Despite this, many manufacturers still continue to use titanium oxide in place of zinc oxide, because it is easier to make titanium oxide micronized and hence invisible on the skin. Zinc oxide, unfortunately, tends to leave a white residue on the skin. The best policy? Find a sunscreen with a mix of titanium and zinc oxides, so you’re covered through the entire spectrum – without necessarily looking like it!

3.) Antioxidants Can Boost Sunscreen’s Efficacy
UV rays are damaging for many reasons, with oxidation being at the forefront. UV light can cause electrons to go haywire, inducing damage in many parts of the cell. It is these compounded disruptions that result in many unwanted signs of aging over time.
Luckily, sunscreen’s UV-blocking powers can be enhanced by using antioxidant serums underneath. For instance, a combination of 15% L-ascorbic acid (vitamin C) and 1% tocopherol (vitamin E) have been shown toboost protection four-fold when applied under sunscreen, in a study published in theAmerican Journal of Dermatologyin 2005.

4.) Retinyl Palmitate in Sunscreen Might Not Be Bad for You
According to alarming research fromtheEnvironmental Working Groupin 2010,skin tumors and lesions developed up to 21 percent faster in mice treated with a 0.1-0.5 percent retinyl palmitate cream. This is certainly disturbing, but other scientists and dermatologists have refuted this finding. Although vitamin A breaks down in sunlight and can potentially form free radicals, most sunscreens with retinyl palmitate include other antioxidants that prevent this from occurring. As Dr. Steven Q. Wang said of the Environmental Working Group study, “It is important to note that the mice included in the […] study are highly susceptible to the impact of UV radiation and can develop skin tumors in the presence of UV exposure within weeks, even in the absence of retinyl palmitate.” Dermatologist Henry W. Lim adds, “When retinyl palmitate is used in sunscreen, it can serve as an antioxidant to improve product performance.”

5.) “Waterproof,” “Sweatproof,” and “Sunblock” are Terms of the Past
All of these words were eliminated from sunscreen bottles in accordance with the new FDA labeling laws, because they simply never made sense. “Waterproof” is a term that misleads consumers into believing they have more sun protection than they really do. No sunscreen is waterproof. Now, products can only be labeled as “water-resistant” for either forty or eighty minutes of swimming or sweating.

As for “sunblock,” nothing ever blocks the sun. Rather, a topical cream can be a physical sunscreen, meaning that it scatters or reflects UV radiation, or a chemical sunscreen, which absorbs UV radiation and then dissipates the radiation as either heat or light at wavelengths that do not perturb the skin. In either case, the key is that these are sunscreens, not sunblocks.

Bottom Line
There’s far more to sunscreen than what is listed on the bottle. It’s unfortunate that more efforts are not directed towards teaching the public what they really need to know to prevent skin cancer and even signs of premature aging, but hopefully this helps somewhat. If you have questions or comments, please continue the conversation with me at Future Derm.

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