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UVA vs UVB
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Find out the difference between UVA and UVB rays, and how to protect your skin from both.

UVA vs UVB Rays: What’s the Difference and Which Type Is More Harmful to Your Skin?

Plus, how to make sure you’re protected from both.

We all know that UV exposure can be harmful to our skin. UV stands for ultraviolet radiation—a form of invisible electromagnetic energy that comes from the sun, as well as man-made sources like black lights and tanning beds.1

There are two different types of UV light that reach the Earth and affect us: UVA and UVB.2 One is primarily responsible for sunburns, while the other is a trigger for skin cancers and premature aging. 

Sunscreens are supposed to protect you from both (that’s why they claim to be “broad-spectrum”), but they don’t always do a good job. In fact, a recent investigation revealed that the most common US sunscreens are inadequate against the most prevalent and dangerous form of UV.3

Shocked? Me too—which is why I created this tutorial. You will learn the difference between UVA and UVB, which one is the most damaging, and what you need in order to protect your skin properly.

What’s the Difference Between UVA and UVB?

UVA vs UVB

Sunlight actually produces three different wavelengths of UV radiation:

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From The Skincare Edit Archives

  • UVA is long-wave radiation between 315 and 400 nanometers (nm)
  • UVB is short-wave radiation between 280 and 315 nm
  • UVC is intensive short-wave radiation between 100 and 280 nm2

Fortunately, we don’t need to worry about UVC, since it is filtered out by the ozone layer and never reaches the Earth’s surface.

UVA and UVB are measured on a scale called the electromagnetic spectrum (which also includes visible light and infrared light). According to the scale, UVA is considered low-energy radiation, since it has longer wavelengths (the distance between peaks in a series of waves). In contrast, UVB is high-energy radiation, since it has shorter wavelengths.

What Is UVA?

When you think of UVA, think “A” for aging. Ultraviolet A (UVA) radiation is chiefly responsible for aging your skin and triggering skin cancers. This is because UVA rays have the longest wavelengths, which penetrate the most deeply. In fact, they go all the way into the dermis, the middle layer of skin, where they cause cellular and DNA damage.4

“UVA rays are the longer-wave rays that do the most harm,” says Dr. Sharyn Laughlin, dermatologist and co-founder of The Sunscreen Company. “According to studies from the past two decades, UVA is the main driver of skin cancer and photoaging.”

When your skin is exposed to UVA, it causes an immediate tanning effect (which is why it’s the type of UV used in tanning beds). However, at the same time, it initiates more insidious changes—like suppressing your immune system, generating free radicals, and interfering with your body’s DNA repair processes.5,6,7

This encourages the eventual formation of wrinkles and pigmentation, as well as melanoma and other skin cancers. You just can’t feel or see the damage right away—which is why UVA is often dubbed “the silent killer.”

What Is UVB?

When you think of UVB, think “B” for burning. Ultraviolet B (UVB) is a higher-energy, shorter-wave radiation that is directly responsible for triggering sunburns.

“UVB rays are the shorter wave rays in the UV spectrum, and are Nature’s warning signal to tell people to get out of the sun,” says Dr. Laughlin. “They penetrate to the epidermis [the outermost layer of skin], and initiate early sunburn.”

Anytime a sunburn occurs, your DNA gets damaged. Fortunately, if you get out of the sun right away, your body is capable of repairing it without consequences like aging and skin cancer.8

But if you stay in the sun—continuing to expose your skin to not only UVB but also UVA—then the UVA will make things worse. “If the individual remains in the sun and receives ongoing exposure to UVA, the DNA damage continues and is more severe: 94% of the mutations of skin cancer are UVA-induced, whereas only 6% are UVB-induced,” says Dr. Laughlin.

In other words, UVB is the main culprit behind sunburns, but in combination with UVA can also trigger DNA changes that play a role in skin cancers.

Is UVA or UVB More Dangerous?

Is UVA or UVB more dangerous

So, which type of UV is worse: UVA or UVB? According to experts, it’s UVA rays that we should be the most worried about.