A Dermatologist Breaks Down the Difference Between UVA and UVB RaysSeptember 15, 2022
You probably know that wearing sunscreen is important, but you may not know the reasoning behind why it’s an essential skincare step. It all comes down to UV rays, which are what cause all the damage to our skin. Too much exposure to UV rays can cause health issues like skin cancer and signs of aging in the skin. And each type of UV ray — UVA, UVB and UVC — has different impacts on the skin.
Here, we talked to board-certified dermatologist Dr. Elyse Love, MD, FAAD about the differences between UVA, UVB and UVC rays, as well as what you can do to protect your skin from their harmful effects.
What Are UV Rays?
Ultraviolet A (UVA) and ultraviolet B (UVB) rays are how the sun makes contact with the earth, and they are invisible to the naked eye. “Sunlight, or solar radiation, is actually a complex combination of multiple types of radiation,” says Dr. Love. “Sunlight contains UVA, UVB, UVC and visible light.”
Dr. Love also notes that UV rays are strongest closest to the equator, at higher altitudes, during the summer and at midday. Plus, snow and water reflect UV rays, essentially doubling exposure.
UV rays have been proven to cause skin cancer, eye damage, a diminished immune system and premature aging in the form of wrinkles, fine lines and dark spots.
The Difference Between UVA Rays and UVB Rays
UVA rays account for 95% of the rays we are exposed to. They’re always present — even on cloudy days — and can penetrate through glass like windows. UVA and UVB light both cause long-term damage to the skin — Dr. Love explains that the main difference is that UVA rays are longer and penetrate to the dermis layer, while UVB rays are shorter and act more superficially.
Both intense one-time exposure to UVA and UVB (think: a sunburn from laying out at the beach) and cumulative exposure to UVA and UVB (think: the amount of sun you get on daily walks to work) can increase the risk of developing melanoma and other types of skin cancer.
“Traditionally, UVA was considered to be the ‘aging rays’ and thought to be more responsible for the development of fine lines, wrinkles, dark spots and redness,” says Dr. Love, “but we now know that both UVA and UVB cause long-term damage to the skin’s DNA that can increase the risk of skin cancer. Both types of radiation also cause signs of skin aging.”
What are UVC Rays?
There is a third type of radiation that we don’t typically hear about. But there’s not much to worry about: “UVC is typically captured by the ozone layer, and does not make it to the earth’s surface,” says Dr. Love.
How to Protect Against UV Rays
The most important thing is to wear sunscreen — and to reapply every two hours or immediately after being in the water or sweating a lot. That also means wearing sunscreen on all parts of your body that are exposed to the sun, not just your face. Dr. Love says that when choosing a sunscreen, you should stick with a broad-spectrum sunscreen that is SPF 30 or higher, like the La Roche Posay Anthelios UV Correct Sunscreen Moisturizer SPF 70.
She also says to take into consideration sun avoidance practices, like avoiding outside activities when the UV index is high (especially from 10 a.m. until 2 p.m. on summer days), wearing a hat to protect the scalp and sunglasses to shield the eyes from harmful rays.
Keeping tabs on the UV index is also a smart habit to get into. “The UV index is a rating scale that rates the level of UV exposure for a region for that day,” says Dr. Love. “The scale ranges from 0 (low) to 11+ (extreme). Sun exposure should be avoided if possible while the index is high.”
Photo: Chaunte Vaughn