With summer comes more time at the beach, the pool, and the outdoors in general. In the United States, 20% of Americans develop skin cancer by 70 years old, and data from American Cancer Society in 2018 show that more people are diagnosed with skin cancer every year when compared to all of the other cancers combined. Now more than ever, it is critical that sunscreen is correctly applied before stepping out into the sun.

In attempting to get the best protection possible, however, we have the tendency to purchase sunscreen products with the highest SPF (I was at fault for this too). SPF stands for Sun Protection Factor, and it is supposed to block the harmful rays of sunlight: UVA (90-95%) and UVB (5-10%) rays.

UVB rays have been accepted to be involved with sunburn and skin cancer. Contrary to popular belief that SPF protects us from both rays, SPF indicates protection from UVB rays and UVB rays only. Furthermore, SPF 100 is assumed to mean two times more protective than SPF 50. In actuality, SPF 50 blocks 98% of the UV rays and SPF 100 blocks 99% - the difference is extremely marginal.

Although a recent clinical trial indicated that "SPF 100+ sunscreen was significantly more effective in protecting against sunburn than SPF 50+ sunscreen in actual use conditions," the authors acknowledge that "single-day exposure may not extrapolate to benefits of longer-term protection." Although it's not clear whether higher SPF is actually worth the extra money, aren't we ignoring a bigger problem here? What about UVA rays that make up most of the sunlight?

The role of UVA rays is less clear than UVB rays, but "recent studies have implicated an increasing role of UVA as a carcinogen likely through its pro-oxidative effects and possibly through other mechanisms such as telomere shortening" according to Amaro-Ortiz et al. in 2014. Environmental Working Group Corporation has also claimed that UVA "penetrates deeper into the skin," and because of the disharmony between protection of UVA and UVB protection, sunscreen with high SPF products actually "offer far less protection against UVA than UVB rays, and this is worst for those products with the highest SPF values." It appears that SPF tells us nothing about how much we are protected from UVA rays, that may be more harmful than the UVB rays.

So, what should we do? The best option appears to be using SPF 50 and reapplying it multiple times throughout the day. For protection against UVA rays, perhaps a push for more research may be the most practical and necessary step.