HomeHealth TopicDermatology

UVA vs. UVB Rays (and Why You Want a Sunscreen That Blocks Both)

Learn the difference between UVA and UVB rays and how the two types of ultraviolet radiation may affect the skin.

Lauren SmithPreeti Parikh, MD
Written by Lauren Smith | Reviewed by Preeti Parikh, MD
Published on April 26, 2021

Sunscreen bottles contain lots of important phrases: SPF, water-resistant, broad-spectrum, and more. You probably know that dermatologists recommend broad-spectrum sunscreen, what does it actually mean? In short, broad-spectrum sunscreen protects against UVA and UVB rays, the two main categories of ultraviolet radiation.

“Broad-spectrum” gets its name because ultraviolet radiation exists on a spectrum of high energy to low energy. Compared to other types of radiation, UV rays exist in the middle of the spectrum. They have a lower energy than x-rays, but a higher energy than radio waves.

Experts further divide the UV radiation into its own spectrum. There are three groups: UVA, UVB, and UVC rays. UVC radiation is the highest energy of the three, but they don’t reach the ground and don’t affect skin health.

The Difference Between UVA and UVB Rays

Both UVA and UVB rays affect the skin, but in different ways.

UVA radiation has the lowest energy within the ultraviolet spectrum. The vast majority of UV rays from the sun that reach the ground is UVA radiation. UVA exposure is primarily linked to aging of the skin. This includes wrinkles, “leathery” skin, and age spots. That said, UVA rays may also have some effect on skin cancer or sunburn risk.

UVB radiation is only a small portion of the UV rays that reach the ground. Still, their effects are dangerous. They have more energy than UVA rays (but not as much as UVC rays). The direct damage they do to the DNA of skin cells increases the risk of skin cancer. They also cause sunburns.

Protecting Your Skin

Broad-spectrum sunscreens help protect against the wide range of rays that can cause skin damage. It’s a well-known fact that sunscreen helps protect against skin cancer and painful sunburns. However, sunscreen is also an underrated anti-aging tool.

Wearing sunscreen consistently is important, but it’s not the only way to keep skin young and healthy. Remember to:

  • Dress in sun-protective clothing, such as lightweight tops with long sleeves and wide-brimmed hats

  • Limit your time outside or seek shade when UV rays are at their strongest (between 10 a.m. and 4 p.m.)

Learn more about preventing skin damage here.

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