The sun is a six billion-year-old star that emits ultraviolet rays, or environmental carcinogens, and UV rays directly contribute to cancer. UV rays are classified into three categories on the basis of wavelength: UVA, UVB, and UVC. UVA rays have the longest wavelength (320-400 nm), and UVC rays have the shortest. UVA and UVB (290-320 nm) rays are the most prominent at the Earth’s surface, and both can lead to undesirable effects on the skin. Short-term consequences of UV exposure include sunburn and tanning, while repeated exposure to the sun and UV light can lead to skin aging and skin cancer. Over the past 100 years, scientists have agreed that the body’s immune system plays an important role in cancer-defense. UV light not only mutates our genetic code but it can also suppress our body’s ability to correct these mutations, a deadly combo.
A Simplified Explanation of UV Ray Interaction with Skin
UV radiation is called a “complete carcinogen,” because it has properties that both initiate and promote cancer growth. The skin consists of two layers: the epidermis and the dermis. The epidermis is the outermost protective barrier, while the dermis houses immune cells underneath the epidermis. This outer epidermal layer accumulates melanin, or pigment, providing protection from UV radiation. Thus, people with more melanin have naturally darker skin and more protection from UV rays. The degree of UV penetration depends on the wavelength. As UVA has a longer wavelength, it will penetrate deeper into the dermis. UVB rays will only penetrate the epidermis. However, both UVA and UVB are capable of causing mutations within DNA, leading to cancer.
One common result of UV radiation is sunburn or inflammation. Specifically, UVB rays can cause swelling of the affected area and cause sunburns. If enough UV damage occurs, the skin cells begin to die.
Tanning occurs when UV rays stimulate the skin cells of the epidermis to produce more melanin. Failure to produce more melanin upon UV exposure has been linked to cancer susceptibility.
The One Fact You Need to Know: UV Rays Can Suppress the Immune System
The immune system is the body’s way of protecting itself from foreign invaders. UVB radiation causes skin cancer. Both short term and long term exposure to UVB rays lead to elevated risk of skin cancer. These rays act by causing mutations within the DNA. The immune system can normally find cells with DNA mutations and remove those cells before they become cancer. In a tumor study, results indicated mice subjected to a lot of UVB radiation had more trouble fighting skin tumors. To explain these findings, the authors suggested that UV rays affect skin healthy by suppressing immune cells and decreases their ability to defend against the tumors.
This ends up as a “double-whammy.” UV light causes mutations but also messes up the body’s ability to find and clear these mutated cells.
Practical Tips About Sunscreens for UV Rays and Skin Health
The ability of sunscreen to protect from the dangers of UV rays depends on three properties: the source of the UV rays, how well the sunscreen stays on the skin, and the effectiveness of the UV rays in causing sunburn. Here are some practical takeaways:
Double-apply your sunscreen: Learn more about what it means to double apply
Buy broad-spectrum sunscreens: Learn how to read your sunscreen labels here
Select the right formulation: Should you buy a lotion, spray, roll-on? Learn more here on which sunscreen formulations may be a better fit.
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