Sunscreen 101: What's the Deal with UVA and UVB Rays?

So we spoke about SPF, but what’s up with UV (ultraviolet)? In short, UV radiation is the sun’s light spectrum that reaches the earth in either UVA, UVB or UVC rays. They come in different wavelengths with UVA being the longest and UVC the shortest (most of it gets absorbed into the ozone layer, so we won’t discuss UVC here). All are invisible to the naked eye, but can result in eye damage, skin aging, skin cancer and more!


So let’s start alphabetically. UVA rays have the longest wavelengths and account for around 95 percent of the UV radiation that reaches the earth’s surface. Although it’s less intense than UVB rays, these are prevalent all day and can pass through cloud and glass. UVA penetrates the skin more deeply and is responsible for premature skin aging, wrinkling and damages skin cells in the epidermis.

If you’re a fan of tanning, then you should also know that UVA rays are what causes it. Your skin actually darkens because of injury to the skin’s DNA, resulting in a tan. With that being said, tanning booths utilize mostly UVA rays. The scariest thing about UVA rays? You can’t see it and you can’t immediately see its damage, unlike with UVB rays.

UVB rays are the main culprit behind skin reddening and sunburns. They damage the skin’s higher epidermal layers and aren’t as common as UVA rays. However, UVB rays vary in intensity depending on season, location, altitude, and even time of day.

In terms of sunscreen, the SPF system mainly measures protection against UVB rays. Now that we know more about UVA rays, “broad-spectrum” sunscreens are available to protect against both.

tl;dr: UVA and UVB rays can cause premature skin aging, eye damage, skin cancer and more! So wear your broad-spectrum sunscreen and stay protected against the sun.