Does sunscreen provide complete protection?

The Sun Protection Factor (SPF) of a sunscreen formula states the effectiveness of this cream when applied at an even layer of 2 milligrams per square centimeter, for blocking the effect of UV sunrays that cause sunburns. The SPF level is defined by comparing the effect of exposure to the sun causing burns to a body area with the evaluated sunscreen compared to the burns to a non coated area. SPF 15 means that compared to a body area without sunscreen, the area with sunscreen will require 15 times more UV to be equally burned compared to the same area without sunscreen.
SPF is evaluated per 2 milligrams of sunscreen per square centimeter, unfortunately most people apply less sunscreen than needed. This causes the SPF value to be reduced dramatically hence the person thinks he/she is protected but in reality the effectiveness of the sunscreen is reduced. Thinking that you are protected when in reality you are not is very dangerous as you might linger in the sun for longer.
Another problem with sunscreens is the fact that many of them protect mostly against skin burning, caused by UV-B.  There are three types of UV rays emitted from the sun, the skin cancer foundation has a good explanation about UV classification on their web site. The different types of UV are: UV-A, UV-B and UV-C. Both UV-A and UV-B pass the ozone layer and reach the earth, most of the UV-C is absorbed by the ozone layer and does not reach us.
UV-A is the most dominant UV radiation reaching us from the sun. It is present throughout the year and during all day light hours. UV-A penetrates glass and clouds and has a deeper penetration depth into the skin than does UV-B. UV-A is a main inducer of skin ageing, wrinkles and skin cancer. It is the main contributor to tanning, it does so by inducing changes in the cell’s DNA, the skin darkens due to synthesis of melanin to protect the skin from further damage form the UV exposure. Tanning salons use mostly UV-A as the tanning source, the intensity in the salons can be 12 times higher than the natural UV-A levels from the sun.
UV-B penetration depth to the skin is superficial and it plays a major role in skin burning. As apposed to UV-A, UV-B is present in lower levels during different hours of the day, different seasons and various locations on earth and it does not penetrate glass. Similar to UV-A, UV-B contributes to skin cancer, and skin ageing.
Sunscreens were created originally to prevent skin burning and to block mainly UV-B. In recent years manufactures of sunscreens have added UV-A protection too, however the level of protection from UV-A is not included in the SPF classification. It is important to verify, when purchasing a sun block, if the formula claims to protect from UV-A and UV-B. If not specified it is probably UV-B protection only.
The problem with sunscreen is that people feel protected from the damaging rays of the sun while they really are not safe. Most people will assume that if they apply sunscreen on exposed areas, they can allow themselves to walk freely in the sun during the extreme UV hours (10AM-4PM). This is a very dangerous assumption as applying the sunscreen needs to be in the correct amount and the sunscreen needs to be of good protection values. In addition, no sunscreen provides complete protection and it is wise to always stay away from exposure during the extreme hours mentioned above.
Another misconception is that after about 4PM and in early morning hours (6AM-10AM) there is no need for sunscreen as the UV radiation is lower. Very wrong assumption! As mentioned above, UV-A is present most hours of the day, so be ware!
Most people are not aware that they need to apply sunscreen when driving or sitting in a car, or if sitting in front of a sunny window at home, the windows will not protect you, (unless they are coated with a UV protection film).
Below are the Prevention Guidelines of the Skin Cancer Foundation for wise protection from the sun:

“Prevention Guidelines
•    Seek the shade, especially between 10 AM and 4 PM.
•    Do not burn.
•    Avoid tanning and UV tanning booths.
•    Cover up with clothing, including a broad-brimmed hat and UV-blocking sunglasses.
•    Use a sunscreen with a SPF of 15 or higher every day.
•    Apply 1 ounce (2 tablespoons) of sunscreen to your entire body 30 minutes before going outside. Reapply every two hours, or immediately after swimming or excessive sweating.
•    Keep newborns out of the sun. Sunscreens should be used on babies over the age of six months.
•    Examine your skin head-to-toe every month.
•    See your physician every year for a professional skin exam.”

If your skin has been damaged by years of exposure to the sun’s damaging rays you might be happy to learn that you can help reduce the damage by treatments offered by various technologies. Sun spots (liver spots) can be removed by skin resurfacing technologies and photo-rejuvenation technologies. In addition, a RF technology exists, that targets reduction of wrinkles, collagen regeneration, skin tightening that improves skin texture and lessens the ill affects caused by UV radiation.  For example, TriPollar RF treatments, have been proven to effectivly reduce wrinkles and tighten the skin.  TriPollar based products are maufactured exclusively by Pollogen Ltd.    You do not have to wait till you are in your forties or later to begin treatments; the earlier you begin the better.
To finalize this write up, it would be nice if we adopted the fashion of un-tanned skin as our ancestors admired during the renaissance and earlier periods. Of course this should not include the discrimination against darker color skin that accompanied the earlier age admiration of non tanned skin.
And finally, if you do spend significant time in the sun, make sure to follow the guidelines mentioned above and minimize the damage to your skin.