What’s the difference between UVA and UVB rays?

If you’re interested in staying safe in the sun, you’ll hear a lot about ultraviolet radiation. That’s because UV rays are the part of sunlight that causes skin cancer and skin aging.

Tanning beds also emit UV radiation. Tanning beds cause the same skin damage as the sun.

It’s helpful to know how these rays work, so you know how to protect yourself. Know your enemy, right?

What is UV radiation?

It may seem odd, but the sun does not emit only one kind of light. Sunlight sends a whole spectrum of light down to us here on Earth.

Some parts of that spectrum of light are obvious to us. Infrared radiation is what heats us up. We may not see it, but we can feel it.

Ultraviolet radiation is at the other end of the light spectrum. Some kinds of insects can see UV, but humans can’t. And we don’t feel it, until it’s too late.

UV radiation can burn and damage our skin without us ever becoming warm. That’s why it is dangerous even on cloudy days.

Not all UV radiation from sunlight makes it to Earth. Most of it gets absorbed by our atmosphere. But two kinds of UV rays do break through. They are called UVA and UVB radiation.

What is UVA radiation?

UVA radiation makes up 95% of the all the UV rays that make it to the Earth’s surface. UVA penetrates deep into our skin and can even pass through glass.

UVA damages your skin, resulting in a tan. It is the primary radiation used in tanning beds. It causes almost all forms of skin aging, including wrinkles. UVA damages the collagen and elastin in the skin and also generates free radicals.

And recent research shows it doesn’t end there.

“UVA partners up with UVB to cause more serious problems, like skin cancer,” says Saira George, M.D., a dermatologist at MD Anderson Cancer Center.

What is UVB radiation?

UVB radiation makes up only 5% of the UV rays from the sun, but it is very high energy.

“UVB does not penetrate as deeply as UVA, but it can wreak havoc on the top layers of your skin.” George says.

UVB damages skin cells and causes DNA mutations that can eventually lead to melanoma and other types of skin cancer.

UVB radiation from the sun also can cause cataracts.  

Cataracts happen when proteins in your eye lens get damaged. The proteins start to collect pigments that cloud your vision.

How to protect yourself

The best way to protect yourself from UV radiation is to stay out of the sun between 10 a.m. and 4 p.m., when UVB rays are at their highest intensity.

It’s important to take care of yourself, even if you are in the shade. UV rays can reflect off surfaces like concrete, water, sand and snow, and still cause significant damage to your skin.

If you do go out in the sun, use a sunscreen with an SPF of 30 or higher. Make sure you choose one that is water resistant and offers broad-spectrum protection.

Broad-spectrum sunscreens reflect and absorb UV radiation. They ensure you are protected from both UVA and UVB radiation. Apply sunscreen at least 30 minutes before going out in the sun and reapply after swimming or sweating.

And don’t underestimate the amount of protection you can get by covering up.

“Clothing can be more reliable,” says George. “A sun protective shirt can really help you fill in the gaps that sunscreen leaves.”

Finally, wear a wide-brimmed hat to shade your head and face, and use UV-protective sunglasses.

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