Sunscreens

The sun emits ultraviolet(UV) radiation(among other emissions such as visible light, etc) in 3 different types, A,B and C. UVC never reaches the earth except in areas where there are holes in the ozone layers, which are naturally occurring at the north and south poles. This is a good thing as UVC is dangerous to all living organisms. UVA and UVB reach the earth in varying amounts depending upon the angle of the sun(strongest when directly overhead). Of the 2, UVA is much more dangerous in that it penetrates deeper in the skin and causes more dna damage than UVB. UVA is also more prevalent than UVB, but UVB has a more rapid effect upon the skin, with the majority of sunburns are caused by UVB exposure. Glass blocks UVB, but NOT UVA. Both UVA and UVB can damage the skin, and both cause skin cancer. When exposed to both, the skin reacts by tanning, which is an attempt by the skin to prevent the UV rays from reaching the nucleus of skin cells, which damages the nuclei. Tanning is an increase in pigment produced by melanocytes which reside in the skin in an attempt to prevent further injury to the cells caused by UV radiation.

Make no mistake, a sun tan represents damage to the skin, and starts the process of premature aging, wrinkles, discoloration, pre- cancers, and finally skin cancers. There is no such thing as a “healthy tan”. 

Tanning beds are almost pure UVA radiation, and are concentrated much more than one could get by natural sunlight, and are therefore more dangerous than sunlight as they accelerate the injury process to the skin. A recent study from the United Kingdom has demonstrated that the risk of melanoma, the deadliest form of skin cancer, increases by almost 2% EACH time one enters a tanning(coffin) bed. In addition, 100% of cancers and pre-cancers of the type called squamous cell carcinoma have damage from UVA exposure as the initiating event. UVB exposure is thought to be more closely linked to basal cell carcinoma, than UVA, but both UVB and UVA cause an increase in skin cancer.

To protect the skin from sun damage when outdoors, you will either need clothing or sunscreen or both. A wide brim hat( solid not mesh)is better than a baseball cap and synthetic material is better than natural (ie cotton), especially when swimming. 100% uv protecting sunglasses are also important(don’t forget the kids!). For years the sunscreens were not uniform in their labeling. Now they have to be standardized. They must all have an SPF rating and broad spectrum protection on their label. THERE IS NO SUCH THING AS A WATERPROOF SUNSCREEN! Most sunscreens are essentially gone after 20-30 minutes of swimming or sweating the equivalent of swimming. Some are allowed to claim water resistance, but at most 40-60 minutes of exposure. SPF(sun protection factor) is a number derived from the length of time it takes to burn after application of the sunscreen. It was originally measured at noon in August in Boston. Now they most likely use artificial UV light sources to measure. For example, if one burns at 10 minutes exposure without sunscreen and applies the PROPER amount of an SPF 30 sunscreen, then one would not burn for 300 minutes of exposure. Broad spectrum protection means that the entire uvb/uva spectrum is covered. The most common errors are not applying enough sunscreen – one ounce is required to cover exposed areas-(which would make an SPF30 really a 10 or 15) and not re-applying after swimming or sweating or after 2 hours. The longer one intends to be exposed, the higher SPF one should apply- gives you more “wiggle room” in case of application error. The sunscreens should be applied at least 15 minutes before exposure.

There are 2 basic types of sunscreen. The first is a chemical screen that absorbs the UV light and converts it to a harmless substance. Oxybenzone is an example. The second is a barrier type which blocks the UV light or reflects it from the skin. The latter is often termed chemical free, and usually comprised of zinc oxide(remember white noses) or titanium dioxide. Most products are a combination of both types to be able to satisfy the broad spectrum requirement. They ALL either degrade or wash off, hence the need for re-application. Creams are the most prevalent type of sunscreen, with solutions, gels, spray, and stick products available. Creams are easier to use on drier skin, solutions and gels better for oily or hair baring skin. Sticks may be easier to use on the face(do not forget lips). While using spray products, DO NOT USE AROUND THE FACE as care should be taken to not inhale the product. Better to spray on your hands and then rub on the skin. If spraying on the skin, ensure that the sunscreen is rubbed in to ensure uniform coating. Infants less than 6 months of age should NOT have sunscreen applied, but rather wide brimmed hats and long sleeve/long pants and under umbrellas. Between 6-18 months sunscreen can be used, but sparingly on skin not covered by long sleeves /pants/hats. Be very careful if using a spray around infants.

Bottom line- the best sunscreen is the one you use, use it right and re-apply!

Author

Robert S. Berger MD Dermatologist