Mohs Surgery & Dermatology Center
The damaging UV radiation in sunlight can lead to many skin problems, including sunburn, age spots, wrinkles, melasma, freckles, allergic rashes, and precancerous lesions called actinic keratoses.
Most importantly, overexposure to sunlight is the major cause of skin cancer, including melanoma. It is important for everyone to be aware of the damaging effects of sunlight and take measures to avoid overexposure.
Although many people enjoy the appearance of tanned skin and think it looks "healthy," tanned skin is damaged skin. The ultraviolet radiation in sunlight penetrates the deepest layers of the skin where it harms the cells. The body responds by making more pigment (melanin) to try to protect itself, but the damage has already happened and may be permanent. The more exposure you have to the sun, the more likely you are to develop skin problems later in life.
The damaging part of sunlight is called ultraviolet radiation, or UV rays. UV is categorized into three types:
The first and more effective way to avoid sun damage is to stay out of tthe sun as much as possible.
If you cannot avoid being exposed to sunlight, there are five basic sun defenses that you should keep in mind when you go outdoors:
In general, UV rays are the greatest between 10 a.m. and 4 p.m. It is best to avoid the outdoors during these hours without protection, particularly during summer, in tropical regions, or at altitude. During this time, you should pay close attention to the appropriate use of sunscreen, clothing, sunglasses, and shade.
You can obtain an accurate measure of the amount of UV rays in your area by looking up the Ultraviolet (UV) Index. The UV Index is like a weather forecast. It provides a report on the amount of damaging UV rays that are expected to affect a region on a particular day. The UV Index changes day to day according to time of year, cloud cover, atmospheric ozone, and other factors.
The following table is a breakdown of the UV Index. A high UV Index number means that you are at greater risk of being exposed to ultraviolet radiation. You should take special care to avoid outdoor exposure to sunlight when the UV Index is moderate or greater.
The UV Index can be found on our Website or in local papers, usually in the weather section.
There are several factors to consider when selecting the appropriate sunscreen for proper sun protection.
Sun protection factor (SPF) - Sunscreens are rated by the amount of protection they provide from UVB, measured as the "sun protection factor" or SPF. Sunscreens with higher SPF provide greater protection from the sun. It is best to use sunscreens that offer a minimum SPF of 15.
Broad-spectrum sunscreens - It is best to use a sunscreen that can protect you from both UVA and UVB rays. These are called "broad-spectrum" sunscreens.
Most of the original sunscreens blocked only UVB, but increased awareness of the damage caused by UVA has lead to the development of ingredients that protect against UVA too. Broad-spectrum sunscreens combine ingredients to provide a product with greater protection.
Common sunscreen ingredients that provide protection from UVB rays:
Common sunscreen ingredients that provide protection from UVA rays:
Sunblocks - "Physical" sunscreen ingredients lie on top of the skin and work by reflecting or scattering UV radiation. They are particularly useful for people who are sensitive to the ingredients found in other sunscreens. Sunblocks often contain one or more of these ingredients:
Although past formulations were unsightly (often leaving a white film on the skin), newer "microfine" formulations are invisible after being applied. Microfine titanium dioxide is effective at protecting from both UVA and UVB rays.
Water resistance - Sunscreens are classified as "water-resistant" if they maintain their protection after two 20-minute immersions in water. They are classified as "waterproof" if they maintain their protection after four 20-minute immersions. You should seek a water-resistant or waterproof sunscreen if you will be participating in water sports, such as swimming or water skiing, or will be actively sweating.
However, independent testing has shown many products do not perform well in the real world. So it remains a good idea to apply sunscreen every time you leave the water, or frequently if you are actively sweating.
Sunscreen should be applied evenly and liberally on all sun-exposed skin within 30 minutes before going outside to give sunscreen time to take effect. (Sunblocks are effective immediately after being applied.) Sunscreens should be reapplied every two hours or following swimming or sweating to ensure effective sun protection. Apply sunscreen generously and reapply frequently at least every two hours.
The chemicals may lose effectiveness over time, so it is important to throw away sunscreen that is past its expiration date or is over two years old.
No sunscreen is 100% effective; take additional measures to avoid the damaging effects of the sun's rays.
Clothing can provide excellent sun protection. However, not all clothing is protective. A thin, wet, white t-shirt will provide almost no protection from UV rays. When selecting clothes for sun protection, consider the following:
Garments fall into 3 categories:
Choose clothing with a UPF rating of at least 15. Keep in mind that the UPF of a garment will decrease over time as the fabric wears.
Overexposure to sunlight can cause cataracts and macular degeneration, a major cause of blindness. Sunglasses can provide effective sun protection for your eyes. However, not all sunglasses are of value. A darker lens itself does not guarantee protection. Look at the label to ensure that the glasses provide UV protection. Sunglasses should be large enough to shield your eyes from many angles. Look for sunglasses that are described as blocking 99% or 100% of UVA and UVB. The glasses may also be described as providing UV absorption up to 400 nm.
If possible, remain in the shade when outdoors. Keep in mind that shade does not provide full sun protection because UV rays can bounce off reflective surfaces, such as sand, snow, water, concrete, or even porch decks. In addition, some fabrics used as shade devices, such as parasols or umbrellas, may not provide sufficient sun protection. If you seek shade under a cloth, look for a fabric that is thick, tightly woven, and dark-colored.
Clear window glass provides protection from UVC and UVB, but not UVA rays. If you are frequently exposed to sunlight while driving, the plastic interleaf of your windshield (which prevents it from shattering) can help block the light, but side windows have no such protection. Non-drivers can make use of additional window shade devices for sun protection. Drivers in some states may be able to use darkly-tinted glass in the side windows, but this is illegal in some states.