UVA vs. UVB: Key Differences and How They Affect Your Skin

When it comes to sun protection, you’ve likely heard about UVA and UVB. Both are types of ultraviolet (UV) rays from the sun and, while they may sound similar, they impact your skin in different ways. Knowing how they work helps you understand why protecting against both is essential for healthy skin.

Exposure to UVA

UVA rays are the most common type of UV radiation you’re exposed to. They’re present year-round during daylight hours and can penetrate through clouds and glass. This means you can be exposed to UVA rays while you’re driving, indoors near a window, or outside — even on foggy or overcast days. UVA exposure can also come from artificial sources, such as tanning beds.

How UVA affects your skin

UVA rays penetrate deep into your skin and cause gradual skin damage, including:

Premature skin aging: Repeated UVA exposure breaks down collagen and elastin, the proteins responsible for keeping your skin firm and resilient. Over time, this leads to:

• Wrinkles and fine lines
• Age spots (also called solar lentigo or sunspots)
• Dry, rough, or uneven skin texture

Tanning and skin cancer risk: A tan forms when UVA rays damage your skin, prompting it to darken as a defense. While it may look harmless, this process still involves indirect DNA damage that builds up overtime and raises the risk of developing skin cancer.

Exposure to UVB

UVB rays mainly come from direct sunlight, especially when you’re outside on sunny days. Their strength varies by time of day, season, and location, but they’re usually strongest in summer (June to September) between 10 a.m. and 4 p.m.

How UVB affects your skin

Unlike UVA, UVB rays only penetrate the surface of your skin. In small amounts, UVB rays help your skin produce vitamin D, a key nutrient that supports bone and muscle health, immune function, and overall well-being.

However, UVB exposure can lead to:

Sunburn: This happens when the skin receives more UVB rays than it can tolerate, leading to redness, swelling, and pain as an inflammatory response. While it may heal over time, each sunburn adds to cumulative skin damage, increasing the risk of skin cancer.

Skin cancer: Develops when repeated UVB exposure damages the DNA in skin cells, causing abnormal cell growth that may eventually lead to the formation of skin cancer. Common skin cancer warning signs include:

• A new mole or spot that appears on the skin
• An existing mole that changes in size, shape, color, or texture
• A spot or nonhealing sore that continues to itch, hurt, scab, or bleed

If you’re unsure about a new or suspicious spot on your skin, visit your primary care provider (PCP) or a dermatology provider.

How to protect against UVA and UVB

To protect your skin daily against UVA and UVB rays:

1. Choose a sunscreen labeled “broad-spectrum,” for protection against UVA and UVB rays.
2. Use a minimum of SPF 30 every day, or a water-resistant SPF 50 or higher for outdoor activities. Apply to all areas of exposed skin and reapply every two hours.
3. Limit time in direct sunlight, especially between 10 a.m. and 4 p.m. when UV rays are strongest.
4. Wear protective clothing such as long-sleeved shirts and wide-brimmed hats, preferably with a UPF rating, and UV-protective sunglasses to help block UV rays from reaching your skin and eyes.

Read more: Protect the Skin You're In

If you have skin concerns or questions about overall skin health, your primary care provider or a dermatologist can help. Find a doctor near you.