SUN DAMAGE, SUNSCREENS AND SUNBLOCKS

By Drs. Gina & Sid Danesh

August 3, 2011

Today more than ever, we know the harsh effects of prolonged sun exposure and to the ultraviolet radiation damage it causes. The sun's rays contain different wavelengths of ultraviolet (UV) light. The two types of UV rays that pass through the earth's atmosphere and cause damage to the skin are UVB and UVA rays.

UVB - are the rays responsible for burning the skin. They effect the outer layer of the skin. UVB is most harmful during the hours of 10am-4pm. UVB passes through the clouds but not through window glass.

UVA - are the rays that we get and do not know we are getting them. They penetrate the skin at a deeper level. They are less likely to burn the skin, but they can age the skin prematurely, cause pigmentation issues as well as change the skin cells DNA - increasing the risk for future skin cancers. UVA rays can travel through window glass and damage the deeper layers of the skin.

Both UVA and UVB light contribute to age-related changes in the skin such as wrinkles, freckles, age spots, and prominent blood vessels. Both UVA and UVB exposure raise the risk of skin cancer. Not everyone knows how to apply sunscreen. Only a small percent of the population uses sunscreen protection and only half of those people apply sunscreen correctly. In addition, regardless of the SPF or what the label says, sunscreens must be reapplied every 80 minutes or less. Sunscreen users mistakenly believe that high Sun Protection Factor (SPF) sunscreen products will protect them all day with one application, when in fact; all sunscreens must be reapplied regularly.

The best way to avoid sun damage is to avoid the sun as much as possible by wearing protective clothing and wide brimmed hats, as well as 100% UV protective sunglasses.

Ultraviolet Protection Factor

Sun protectiveness of clothing can be evaluated and rated with a measuring system called Ultraviolet Protection Factor (UPF). UPF is a similar concept to SPF; however, UPF rates both UVA and UVB protection, whereas SPF only rates UVB protection. In 1996, the term UPF was devised in Australia as a measure of how much UV penetrates a fabric.

UPF is determined by using a UV transmittance analyzer to gauge the spectral transmission of UVB and UVA through a fabric. If a fabric is rated UPF 30, then it is absorbing or blocking 29 out of 30 units of UVR, or 97 percent of UVR. This is the same level of protection provided by an SPF 30 sunscreen that is used properly. To achieve a UPF, a fabric must undergo 40 simulated launderings, be exposed to the equivalent of 2 years of light exposure and be tested with chlorinated water if it is intended for swimsuits.

Today, many manufacturers offer special UV-absorbing clothes, from swimsuits and shirts, to hats and pants. This clothing will usually have a high UPF rating, indicating how much UVR it absorbs. These clothes have special weaves, and are treated with UV-absorbing chemicals such as titanium dioxide.

To be deemed sun-protective, such clothing must have a UPF of more than 30 and retain its sun-protective qualities after numerous washings and exposure to sunlight.

White and see through shirts have a low UPF, less than 5. However, darker clothing could provide much better protection.

Another way to protect oneself from sun damage is applying sunscreens and sunblocks.

The question of chemical versus physical block is important. Chemical sunscreens are often unstable after exposure to UV light and degrade over time. Sunscreens are less visible on the skin and are designed to protect against UVA, UVB, or both. They do allow some radiation through and need to be reapplied every few hours because their ingredients break down after exposure to sunlight. If you use sunscreen, it is better to use one that has a SPF 30, put on a lot, and reapply every two to three hours.

Some of the better spectrum coverage sunscreen ingredients include Avobenzone (Parsol 1789), Oxybenzone, Helioplex, and Mexoryl.

The better physical blocks are zinc oxide and titanium dioxide with zinc being superior in broad spectrum protection. These physical blocks are opaque and reflect and scatter light and act as a mirror on your skin to block entry of almost all of the sun’s UVA and UVB rays into the skin.

Look for SPF 30, which will block 97% UV rays but also look for zinc oxide in greater than 3% to provide coverage of UVA light and better overall protection.

• In summary, Always make sure that your sunscreen is SPF 30 or higher, and “broad-spectrum” which covers both UVA and UVB rays.
• A generous amount of sunscreen should be applied to all exposed skin (do not forget your ears and the back of your neck.) In the summer, it is recommended to use one ounce of sunscreen – (5-6 teaspoons) of sunscreen is recommended to cover the entire body.
• Sunscreens that contain chemical absorbers will need to be applied a half hour before sun exposure to allow the active ingredients to go to work in the skin and form a protective shield. Physical sunscreens (such as titanium dioxide or zinc oxide) will shield the skin immediately.
• Be sure to reapply another layer of sunscreen if you will be in the sun for more than 2 hours throughout the day under intense UV conditions, and especially when it’s windy or you’re sweating.

Whether you choose a lotion, stick, gel, or cream sunscreen depends largely on your skin type and personal preference. Oil-free (non-comedogenic) gels are good solutions for facial skin prone to breakouts, and sprays may make application to the back and shoulders easier. While being applied, aerosol sunscreens can lose much of their protection during the transfer from the bottle onto the skin. This is because not all of the molecules land on your body.

SPF- Sun Protection Factor

SPF measures the time taken to burn when out in the sun. It does NOT measure the level of protection against UVA rays at all.

SPF stands for sun protection factor. The SPF numbers on a product can range from as low as 2 to as high as 100. These numbers refer to the product's ability to screen or block out the sun's burning rays. The SPF rating is calculated by comparing the amount of time needed to produce sunburn on protected skin to the amount of time needed to cause a sunburn on unprotected skin. The higher the SPF, the greater the sun protection. However, it is a common mistake to assume that the duration of effectiveness of a sunscreen can be calculated simply by multiplying the SPF by the length of time it takes for him or her to suffer a burn without sunscreen, because the amount of sun exposure a person receives is dependent upon more than just the length of time spent in the sun. The amount of sun exposure depends upon a number of factors including the length of exposure, time of day, geographic location, and weather conditions.

No sunscreen blocks 100 percent of Ultra Violet (UV) rays. SPF 15 can protect against 93 percent. SPF 30 protects against 97 percent. SPF 50-60 shuts out 98 percent. The higher the SPF the more harsh chemicals are in the product. SPF 30 provides skin with 97% protection, where as SPF 60 provides skin with 98-98.6% protection. There is less than 1.6% difference in protection factor. A SPF 60+ needs more chemicals to achieve a higher SPF, potentially putting more toxins in your body.

Currently, the FDA is banning the word "waterproof." Now the term, "water/sweat/perspiration resistant" is accurate, however; this only means the sunscreen offers SPF protection after 40 minutes of water exposure. So to be safe, use this basic rule of thumb: re-apply often.

Powder Sunscreen is becoming very popular for a number of reasons. One of the biggest reasons is to have a more natural SPF with fewer to no chemicals. There are several powder sunscreens on the market today. The most important aspect of any powder sunscreen is that it offers broad-spectrum protection.

Vitamin D, calciferol, is a fat-soluble vitamin. It is found in food, but also can be made in your body after exposure to ultraviolet rays from the sun. Fortified foods are the major dietary sources of vitamin D. Exposure to sunlight is an important source of vitamin D. Ultraviolet (UV) rays from sunlight trigger vitamin D synthesis in the skin. Use of sunscreens do not totally block the effects of Vitamin D in the body. It is especially important for individuals with limited sun exposure to include good sources of vitamin D in their diet.

FUN FACTS

• Sunscreens do expire. They lose their effectiveness. You should replace your sunscreen every summer.
• Dark skin individuals also need sunscreen. Skin cancer rates are increasing amongst darker skinned individuals. And, the sun deepens dark spots and can lead to hyperpigmentation. So all individuals need to apply broad spectrum sun protection.
• Combination sunscreens and insect repellants are not feasible. Much more sunscreen is needed than the repellant and therefore the amount of repellant can become toxic.
• Tanning salons are not safe. They use UVA rays which can also increase the chances of skin cancer. So best to totally avoid tanning salons.
• Using lip balms with sunscreens are a very useful way of preventing cancer of the lips. But we doubt sunscreen for the hair and nails have any real value.
• The new sunscreens with SPF 100 are not any better than SPF 30 which block 97% of UVB rays.
• To increase compliance, SPF protection in cosmetics have helped. Most important is to reapply. When wearing make-up, reapplying powder sunscreens are preferable.
• On cloudy days, 80% of UV rays go through the clouds. So regardless of the weather, sunscreens need to be used daily. Snow and sand also can reflect UV rays, so in these situations, sunscreens need to be used religiously.
• For Children, using sunscreens that are chemical free are safer such as ones with zinc oxide or titanium dioxide which are also less irritating. All children over the age of 6 months need to use sun protection regularly.

Main points to take from this article are to use sun protection, sun blocks and sun screens regularly and generously.