The Green Beauty Guide

When I wear sunscreen, I hope it’s blocking harmful UV rays, so is there any difference between sunblock and sunscreen? Apparently, there is.

            True to its name, sunblock reflects the sun’s rays, thereby blocking them from reaching your skin. Sunscreen absorbs rather than reflects ultraviolet (UV) radiation, explains Harvard Medical School report.

            Sunblocks, such as zinc oxide and titanium dioxide, are highly effective in protecting against both UVA and UVB rays, the types of UV radiation that cause sunburn and skin cancer. Sunblocks often appear white on the skin.

            Sunscreens tend to be less visible on the skin. They usually contain benzophenones, which protect against UVA, and cinnamates and salicylates, which protect against UVB. You’ll see these ingredients listed as oxybenzone, octyl salicylate, or octyl methoxycinnamate, to name a few. A major drawback of these sunscreen ingredients is that they often break down after several hours of exposure to sunlight, which means you need to reapply them.

            The American Academy of Dermatology recommends using sunscreen with an SPF rating of at least 15. People with fair skin or at high risk for skin cancer may want to go higher. The higher a sunscreen’s SPF rating, the longer it protects against sun exposure. Products labeled “broad spectrum” often contain several different sun protection ingredients in order to cover a broad range of UV radiation.

            Two new chemical sunscreens—Anthelios SX (a combination of  Octocrylene, Parsol (avobenzone) and Mexoryl SX) and Helioplex (blend of Avobenzone and Oxybenzone) —provide longer-lasting protection against UVA and UVB rays. Research shows that Anthelios SX, which was approved by the FDA in 2006, retains 80% of its UVA protection and 90% of its UVB protection five hours after application. Mexoryl is important in impeding ultraviolet A light, potentially reducing many of the characteristics of skin aging and preventing biochemical changes that can lead to nonmelanoma carcinoma.  However, such benefits are not without health risks.  Mexoryl, chemically known as terephthalydene dicamphor sulphonic acid, does protect against cytotoxicity and genotoxicity of solar UV radiation. However, there’s a bit of chemistry needed to explain how it works.

            Mexoryl may be the perfect sunscreen in a dermatologist’s dreamworld, especially since L’Oreal’s own studies provided with all the safety data the dermatologist needs to know (An in vitro strategy to evaluate the phototoxicity of solar UV at the molecular and cellular level: application to photoprotection assessment. Marrot L, Belaidi JP, Chaubo C, Meunier JR, Perez P, Agapakis-Causse C. L’Oreal Advanced Research, Life Sciences Research, Central Department of Product Safety). but the facts suggest otherwise.

            First, even the now-ancient avobenzone (trade-named Parsol 1789)’s UVA absorption spectrum is actually broader than Mexoryl’s  and coming close to zinc oxide which seems to ward off all possible variations of sun radiation. Second, while Mexoryl is supposed to be more UV-stable than other sunscreens, sunscreens must be reapplied because they disappear from the skin due to our beach activities such as swimming, playing volleyball, running, building sand castles  - you know the drill.  The level of stability isn’t publicized for comparison, either, so what exactly does ‘more stable’ mean, five seconds more stable?

            To me, the most troubling point is formulation of Mexoryl-containing sunscreens. Since it’s a di-sulphonic acid compound with a native pH of 1 - that’s more acidic than your stomach!– - it needs to be neutralized with something as strong and potentially carcinogenic as triethanolamine. No wonder most sunscreens containing Mexoryl also contain tons of potentially toxic petrochemicals.

            Mineral sunscreens, such as titanium dioxide and zinc oxide, are also called physical sunblocks. Compared to zinc oxide from the point of sun radiation blockage, Mexoryl looks quite inferior, especially considering all issues of health safety, stability and spectral absorbance.  

            Today, the reliable UV filter should be heat and photostable, water resistant, nontoxic, and easy to formulate. The newer studies suggest that vitamins A, C and E combined with photostable mineral UV-filters provide virtually perfect sun protection. So when you head on shopping for the new sunscreen, avoid all PABAs and other chemical sunscreens. Look for plain old titanium dioxide, zinc oxide, vitamins A, C, E, allantoin, and squalane - the latter two are also capable of absorbing sun radiation.

            I know, I know. Zinc oxide creams are so heavy and greasy. But you can always shower afterwards. And you can always comfort yourself with knowing that you have just absorbed a good deal of immune system boosting, brain clearing, acne fighting mineral. That feels good, doesn’t it?

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