Striking, Isn't It?

Maybe you have seen it before, but this photo is not photoshopped! This is the image of a 69-year-old male which was published in the eminent New England Journal of Medicine in 2012. He was a delivery truck driver for 28 years; every day for 28 years, ultraviolet A (UVA) rays transmitted through the window glass of his driver's seat caused these changes to his skin. This is called photoaging. Due to chronic sun exposure, this man looks and his skin literally IS, much older on the left side of his face.

The Truth About UV Rays

Our beautiful sun emits ultraviolet radiation, two types that reaches us on Earth. The first type are long wavelength (315-400nm, for those who want to know) ultraviolet A (UVA) rays and the second type are shorter wavelength (280-315nm) ultraviolet B (UVB) rays.

UVA rays reach the deeper portion of the skin called the dermis whereas UVB rays are mostly absorbed by the more superficial skin, called the epidermis, as well as the upper dermis.

Photo Credit: Coelho MMV, Matos TR, Apetato M. The dark side of the light: mechanisms of photocarcinogenesis. Clinics in Derm. 2016;34:563-570. — Photo Credit: Coelho MMV, Matos TR, Apetato M. The dark side of the light: mechanisms of photocarcinogenesis. *Clinics in Derm.* 2016;34:563-570.

Exposure to UVB rays is associated with photocarcinogenesis = skin cancers. Although UVB rays are thought to be 1000-10,000 times more carcinogenic (cancer-causing) than UVA rays, UVA rays have also been shown to cause skin cancer. The mechanism is related to direct DNA damage as well as suppression of our immune system, or the body's ability to resist cancers!

UVA rays are more often implicated in photoaging = aging related to sun exposure. Complicated story made simpler, UV radiation results in the formation of reactive oxygen species (ROS), which damages cells and results in dreaded collagen breakdown. We all know what that looks like: fine wrinkles, thin, dry, and leathery skin, skin laxity, and development of benign overgrowths such as seborrheic keratoses (Consult Dr. Google, go for it).

Medical students often learn a mnemonic: "UVA ages, UVB burns." But don't be fooled as UVA and UVB rays have BOTH been associated with photoaging and photocarcinogenesis.

WTF, SPF?

Now that I have freaked you out about the harmful effects of UV radiation exposure...let's talk about how we can protect the largest organ of our body, our skin. I want to spend the rest of this post discussing sunscreen.

SPF stands for sun protection factor. Sunscreens are classified by an SPF number, which is primarily a measure of the UVB protection offered. In the USA, UVA protection is assessed with the critical wavelength method. Long story short, a sunscreen must be labeled as "broad-spectrum," to meet the Food and Drug Administration's (FDA) requirements for both UVA and UVB protection.

A sunscreen that is NOT broad-spectrum and predominantly UVB-only provides a false sense of security on photo-protection -- although the user may be less likely to develop a symptomatic sunburn, they are still being fully exposed to photoaging and photocarcinogenic UVA rays. Meaning: still at risk but no sunburn to show for it.

The #1 Thing You Need Everyday

Sunscreen is the number one product you need for your skin. Every. Single. Day.

Below is a helpful infographic from the American Academy of Dermatology on how to select an effective sunscreen:

Photo Credit: American Academy of Dermatology; <https://www.aad.org/public/spot-skin-cancer/learn-about-skin-cancer/prevent/how-to-select-a-sunscreen

And here is a video from the American Academy of Dermatology on "How to Apply Sunscreen," because how you apply it does affect how well it protects you.

Prevention Is The Best Treatment

May is Skin Cancer Awareness Month. But really, every day should be a skin cancer and (anti-aging) awareness day. Take 30 seconds today to apply, and reapply. Prevention is the best treatment!

References
1. Gordon JRS, Brieva JC. Unilateral dermatoheliosis. N Engl J Med. 2012;366:e25.
2. Coelho MMV, Matos TR, Apetato M. The dark side of the light: mechanisms of photocarcinogenesis. Clinics in Derm. 2016;34:563-570.
3. Mancuso JB, Maruthi R, Wang SQ, et al. Sunscreens: an update. Am J Clin Dermatol. 2017 May 16. [Epub ahead of print]
4. American Academy of Dermatology website

By Leslie Kim, MD, MPH - Co-Founder and Facial Plastic Surgeon