Most people who go out into the sun wearing sunscreen and don’t end up with a sunburn probably think their skin was adequately protected.
This is often far from the truth. Here’s why.
First, many sunscreens contain anti-inflammatory chemicals that can prevent a sunburn from forming even if they’re applied after you’re home from the beach. In the absence of the warning sign that a painful sunburn provides, sunscreen users can falsely assume they were fully protected from the harmful effects of UVB rays, when in fact they essentially were duped by a chemical trick.
Second, many sunscreens don’t provide adequate protection from UVA rays. Higher-energy UVB rays are the primary cause of sunburns and pre-cancerous DNA mutations, but UVA rays cause more subtle damage. They penetrate deeper into skin tissue and are most responsible for generating free radicals – energized molecules that are highly reactive and can damage DNA and skin cells (Marrot 2005), promote skin aging (Wlasckek 2001) and cause skin cancer (Wittgen 2007).
Laboratory tests show that most of the FDA-approved UV filters in sunscreens release skin-damaging free radicals when struck by UV radiation (Allen 1996, Beeby 2000, Cantrell 1999, Damiani 2007 Damiani 2010, Dondi 2006, Hidaka 2006, Knowland 1993, Sayre 2005, Serpone 2002). This is a deliberate strategy for diffusing the intense energy of UV rays, but it also suggests that sunscreens should be carefully formulated and tested to ensure they offer the strongest and most lasting protection from the damage of free radicals.
Laboratory testing to measure free radical generation has shown that fewer free radicals form in sunscreen-protected skin than in unprotected skin. In other words, sunscreens typically do more good than harm in preventing UV-induced free radicals. (Popov 2009, Serpone 2006, Haywood 2003). But they should be better.
One study found a 45 percent reduction in formation of free radicals when sunscreen was used in typical amounts, and a 55 percent reduction when it was used at the recommended amount – two milligrams per square centimeter of skin (2 mg/cm2). Translated to an SPF-style index, this would be equivalent to a “free radical protection factor” of 2, in contrast to the common sunburn protection factors (SPF) of 15 to 50 (Haywood 2003). Follow-up studies measured free radical protection factors of around 2-to-4 in SPF 15 sunscreens containing either avobenzone or titanium dioxide for UVA protection (Haywood 2012).
European sunscreens provide greater free radical protection because they contain superior ingredients. In tests, 12 European sunscreens averaged a free radical protection factor of 13 (Wang 2011). In a follow-up study of European products, three sunscreens with inadequate UVA protection provided the least free radical protection (Wang 2012). Adding the antioxidant vitamins C or E to the sunscreens had no protective effect against free radical formation.
Applying too little sunscreen or reapplying it too infrequently also diminishes protection against free radical formation. Consumers commonly apply a much thinner coating of sunscreen than recommend on the product label. One study of three common sunscreen ingredients found that after one hour of UV-exposure, the number of free radicals on sunscreen-treated skin was actually higher than on untreated skin (Hanson 2006), suggesting that reapplying sunscreen frequently is essential.
The sunscreens with the best UVA protection are also best at suppressing free radical formation (Wang 2012), but inadequate UVA protection is a persistent problem in products sold on the US market. UV rays quickly break down avobenzone, the most common UVA filter in American sunscreens, unless it is mixed with a stabilizer. Furthermore, FDA’s weak regulations allow nearly every sunscreen to claim “broad spectrum,” or UVA, protection, even though some are much better than others. These weak rules give manufacturers little incentive to improve their products.
The bottom line is that to be truly effective at preventing skin damage and cancer, U.S. sunscreens will need to provide better protection from UVA rays. This will not happen until FDA sets higher requirements for UVA protection and approves the use of modern sunscreen ingredients with superior UVA filtering and stability. FDA should also ban the sale of sunscreens that provide poor UVA protection or approve a labeling system that classifies UVA protection as low, medium or high to enable consumers to choose the best products.
In the absence of truly protective regulations, consumers are in the worst possible position: Thinking that their sunscreen is providing more protection than it really is, they stay out longer in the sun and thereby increase their risk of skin cancer and skin damage.