UV Radiation and Sunscreens

Exposure to ultraviolet (UV) radiation from the sun is the most common cause of skin damage, including collagen disruption, free-radical formation, DNA repair interference, and immune-system inhibition. A few simple facts about UV radiation and sunscreens will help you to protect yourself.

UV Radiation

There are two types of UV radiation that have an impact on our skin:

UVB Radiation, with a wavelength of 290-320 nanometers, is what causes sunburn on the top layer of the skin, the epidermis. The intensity of UVB radiation corresponds to the intensity of sunlight: The highest levels occur in the middle of a summer day.

UVA Radiation, with a longer wavelength of 32-400 nanometers, is to blame for most extrinsic skin aging. The longer UVA rays penetrate the epidermis and affect the lower layers of the skin. The ambient level of UVA radiation is basically constant: Your skin can be damaged even on a foggy winter morning. Unlike UVB, UVA rays penetrate glass.

Exposure to the UV radiation in sunlight ages your skin, causing wrinkles, blotches, and thinning. Fair skin is most vulnerable to damage, but all skin is affected. Proper use of a good sunscreen can protect your skin.

Using Sunscreens to Protect Your Skin

Sunscreens fall into two basic categories:

Physical Blocks, including titanium dioxide and zinc oxide, are effective for both UVA and UVB. Although you do see people with white noses, both of of these blocks are also available in a clear form. If your skin is particularly sensitive, you may want to look for a sunscreen that contains only one or both of these active ingredients.

Chemical Blocks absorb either or both UVA and UVB radiation. There are a number of different chemical blocks available, and they are sometimes used in conjunction with physical blocks. A good product will list ingredients and tell you what radiation wavelengths it is intended to block. The best sunscreen choice should be one that protects you from both UVA and UVB radiation.

The SPF number is a helpful indicator, but it does not give you sufficient information to choose a sunscreen. SPF relates only to UVB protection and only tells you how long you can stay in the sun before you get a sunburn. For example, if you can stay in the sun for 20 minutes before you begin to burn without sunscreen, then an SPF-15 sunscreen should protect you 15 times longer, or 5 hours. A higher SPF number doesn’t give you more protection, it just extends the time you can stay in the sun. It also tells you nothing about UVA protection.

There are a variety of special sunscreen formulations for things like dry, oily, or blemish-prone skin, specific facial use, and so on. You can get formulations for people who exercise vigorously or immerse themselves in water. Some are dual-duty sunscreens and moisturizers. Others combine tint, topical medication, or makeup foundation with sunscreen.

To be effective, sunscreen should be applied in an unbroken protective film. Because sunscreen is partially absorbed and disperses more evenly with time, you should apply it at least 20 minutes before exposure to the sun. In general, you should apply sunscreen over anything else you apply to your skin, such as moisturizer or foundation, so you don’t dilute the sunscreen. An exception is high-SPF loose powder, which you can use to set the sunscreen and ensure a matte finish. Finally, if you are swimming, exercising vigorously, or otherwise compromising the protective film, you will need to reapply your sunscreen more often.

Make sunscreen application part of your daily routine, all year round. In the morning, and as appropriate throughout the day, apply your sunscreen, regardless of how much time you expect to spend outside. Although clothing that covers more skin rather than less also provides a measure of protection, be aware that your skin can be damaged through fabric, too.

Various cosmetic treatments and topical or oral medications can make your skin even more vulnerable to the damaging effects of UV radiation. We will be happy to teach you how and when to apply extra protection, and we can also recommend the highest-quality sunscreens most suited for your particular skin type. You can purchase highly-rated products from our office.

 

 

 

 
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Phone: 408-866-4884 Barry Press, MD • Wendy Holmes, RN