UV Rays & How the Sun Can Damage Your Skin

Exposure to ultraviolet (UV) radiation, either from the sun or tanning beds, is a leading cause of skin cancer. For the majority of people, exposure to UV radiation comes mainly from sunlight.

With the classification of UV radiation as a human carcinogen by the World Health Organization, it is important to understand how exposure to skin damaging rays increases skin cancer risk and what you can do to minimize that risk.

Sunlight is made up of three types of harmful rays:

• Ultraviolet C (UVC)
• Ultraviolet B (UVB)
• Ultraviolet A (UVA)

UVC rays have the shortest wavelength. While they are the most powerful and potentially harmful, UVC rays are absorbed by the ozone layer and don’t reach the Earth’s surface in large enough doses to impact our skin significantly.

UVA and UVB rays are a different story. Both penetrate the atmosphere and can be harmful to your skin, including increasing your risk of developing skin cancer.

UVB rays have a shorter wavelength and don’t penetrate as deeply into your skin, but can cause more direct tissue damage.

Overexposure to UVB rays causes sunburns and damages the epidermis—the visible top layer of the skin. It can also damage and alter the DNA of skin cells, increasing the risk of skin cancer.

UVB intensity varies geographically and may be more or less intense depending on the season and time of day.

UVA rays have the longest wavelength and are not absorbed by the ozone layer. UVA radiation is what gives people a tan (except those with lighter skin, who simply burn). It also causes premature aging and suppresses the immune system. UVA rays alter the DNA of skin cells in the dermis, making it more difficult for your body to fight off cancer-causing changes.

Your skin is the largest organ of the human body. Along with being the largest organ, skin is a protective casing that covers your entire body. The amount of skin on the body of the average human adult stretches more than 20 square feet and weighs roughly eight pounds!

Skin does a long list of critical jobs that keep you alive. Along with keeping your insides on the inside, your skin:

• Shields your fragile internal organs from inhospitable environments
• Helps regulate your body temperature by keeping you warm or cool
• Contains the nerve cells that create your sense of touch
• Keeps out microbes like bacteria that might make you sick
• Blocks harmful ultraviolet (UV) radiation from the sun

Unfortunately, protecting your internal organs from UV rays comes at a cost. Anyone who has forgotten to put on sunscreen and spent a little too long outside knows the symptoms that appear when UV damage has occurred: your skin becomes tight, painful, and burnt.

But while sunburns are painful and unsightly, they are far from the most dangerous aspect of UV radiation. After the sunburn fades, severe UV radiation damage and/or long-term sun exposure can alter our DNA and cause us to develop skin cancer.

UVA and UVB rays affect the skin in different ways.

UVA radiation penetrates more deeply into the skin than UVB radiation and is responsible for the skin changes attributed to premature aging, such as wrinkles. Recent research indicates that UVA radiation plays more of a role in the development of skin cancer than previously thought. You can download our Skin Cancer Self-Exam Checklist as a first step if you have concerns about skin cancer.

UVB radiation affects the upper layers of skin and is primarily responsible for changes to the surface of the skin, such as the reddening and darkening of the skin associated with sunburns and suntans. UVB radiation also stimulates vitamin D production in the body, but prolonged exposure provides more damage than reward.

Both types of UV rays damage the DNA of skin cells. This UV damage can lead to the skin cell mutations that cause skin cancer. In addition to skin cancer, UV radiation exposure can also cause premature aging, immune suppression, and irreversible eye damage.

Protecting your skin from harmful UV radiation requires a multi-layered approach. No single method provides complete protection against skin damaging rays, so combining several strategies offers the best defense against skin cancer, premature aging, and other UV-related damage.

UV rays are strongest between 10 a.m. and 4 p.m. year-round, even during winter months. Seek shade during these peak hours whenever possible. Remember that UV radiation can penetrate clouds—more than 75% of UV rays make it through cloud cover—so protection is necessary even on overcast days.

Beach umbrellas, tents, and other portable shade structures can provide valuable protection during outdoor activities.

While sunscreen is essential, clothing provides your first line of defense against UV radiation:

• Fabric choices: Choose tightly woven, dark-colored fabrics when possible
• UPF-rated clothing: Look for clothing labeled with UPF (Ultraviolet Protection Factor) ratings—many manufacturers now offer lightweight, tightly woven options with special UV-blocking treatments
• Hat protection: Wear wide-brimmed hats to protect your face, ears, and neck
• Eye protection: Use UV-blocking sunglasses to protect your eyes—melanoma can develop in the eyes if left unprotected
• Coverage awareness: A standard cotton t-shirt provides less protection than SPF 5 sunscreen, well below recommended levels

Sunscreen is one of the most useful tools in combating UV radiation, but choosing and using it correctly is essential:

• Select broad-spectrum sunscreen with SPF 30 or higher that protects against both UVA and UVB radiation
• Always check expiration dates—expired sunscreen loses its protective power over time
• Consider your skin type, geographic location, and planned outdoor activities when selecting products

Most people don’t use enough sunscreen or apply it correctly, significantly reducing its effectiveness:

• Timing: Apply sunscreen 15-30 minutes before sun exposure
• Amount: Use at least one ounce (approximately 3 tablespoons) for full body coverage
• Complete coverage: Don’t miss commonly overlooked areas including ears, tops of feet, backs of knees, back of neck, back of hands, and scalp (especially for those with thinning hair)
• Under makeup: Sunscreen can be applied under makeup for daily protection
• Reapplication: Reapply every 2 hours, or every 90 minutes if swimming or sweating heavily

UV protection is necessary throughout the year. UVA rays can penetrate glass and clouds, making protection important even indoors near windows and on cloudy days. If possible, avoid prolonged time outdoors during peak hours of sunlight, particularly in the summer.

The sun’s UV radiation poses real risks to skin health, from painful sunburns to serious skin cancer. However, protecting yourself is straightforward when you understand what works.

Effective sun protection combines multiple strategies: applying broad-spectrum SPF 30+ sunscreen correctly and regularly, wearing protective clothing and accessories, seeking shade during peak hours (10 a.m. to 4 p.m.), and avoiding tanning beds entirely.

Remember that UV rays can be harmful year-round, even on cloudy days and through windows. By making sun protection a daily habit rather than just a beach-day consideration, you can enjoy outdoor activities while maintaining healthy skin and significantly reducing your skin cancer risk.