Some Ultra Violet Radiation (UVR) facts:

UVR is strongest between 10:00AM and 2:00PM. Clouds filter some but not most of the UVR so it's still possible to get burned on a cloudy day. Some ground surfaces such as sand and snow reflect most of the UVR. For instance snow can reflect as much as 80% on the incident UVR Water actually reflects very little UVR. For every 1000 feet increase in altitude the UVR increases by 4%.

Sunburn

Sunburn is caused by overexposure to UVR, mostly UVB. In fact, sunburn is almost exclusively a UVB phenomenon.This is important because it means that the SPF system measures UVB protection and not UVA (see SPF below). During a sunburn the skin turns red, swells and, in severe cases, blisters. On a cellular level there is an increase in inflammatory cells as well as many chemicals associated with inflammation. A sunburn continues to develop for 12 to 24 hours after the exposure. One blistering sunburn will double a person's chance of developing skin cancer. Remember however, that avoiding sunburn is not the same as avoiding sun damage. Sunburn is just the immediate sign of UVR overexposure. People who have never been sunburned can still develop the delayed problems such as skin cancer and the sun related skin changes such as deep lines, sagging skin . . .


Skin type

The Skin Type system is a method commonly used to assess one's sunburn risk. There are 6 (1 - 6) skin types (see below). The lower numbers represent those people more likely to burn and the higher numers are reserved for those people with a greater degree of natural protection. As we all know, fair skinned, light eyed people with freckles are the most sun sensitive while dark skinned dark eyed are the least sun sensitive. Everyone else is somewhere in-between. Again, it is important to remember that, while avoiding a burn is important, it does not mean that you have escaped more serious damage that can lead to damaged skin and even cancer.
Type 1 - Always burns, never tans
Type 2 - Usually burns, tans with difficulty
Type 3 - Sometimes burns, sometimes tans
Type 4 - Burn minimally, always tans
Type 5 - Rarely burns, tans profusely
Type 6 - Never burns, deeply tans


SPF

SPF stands for Sunscreen Protection Factor. It is measured by determining how long a given person takes to "burn" with and without the sunscreen product on. If it takes 10 times longer with the sunscreen product then that product has a SPF of 10. If it only takes twice as long then that product has an SPF of 2. In reality, the testing labs don't really burn the test subjects they just give them enough UVR to cause the skin to turn barely red. This minimum dose is called the MED (minimal erythermal dose).

Sunscreens

Sunscreen are chemicals that, when applied topically, keep UVR from reaching your skin. They work either by absorbing the UVR or by reflecting it. Either way, if used properly, they can keep a lot of UVR from reaching you. There are two types of sunscreens: organic and inorganic (also called physical). Organic sunscreens have been the mainstay of commercially available products for years. The term "organic" simply means that these sunscreens are composed of, among other things, carbon and hydrogen. It does not mean that they are naturally occurring and, in fact they are not. Organic sunscreens are relatively complex molecules that are to some degree absorbed into the skin.

The most famous sunscreen is PABA (para amino benzoic acid). PABA became so well known because a significant number of people turned out to be allergic to it. Most products are now "PABA Free" but many people still have problems with one or another of the organic sunscreens. For example, Benzophenone (Oxybenzone) is an organic sunscreen that is commonly used. It is probably the one most associated with adverse reactions. Physical sunscreens are actually microscopic solid pieces of sunscreen. Zinc oxide and Titanium dioxide are the two that are commonly used. Most people associate zinc oxide with the white thick paste lifeguards used to use. It was know to be the best sun block available but it was cosmetically unacceptable and therefore used only by lifeguards or skin cancer patients.

Fortunately, things have changed and you can now get physical sunscreens that are transparent. Zinc oxide, for example, is now manufactured so that the particles are so small that you can not see them. These space age physical sunscreens are referred to as microfine powders and Z-COTE (microfine zinc oxide) is an example. The sunscreen manufacturers now use Z-COTE and other microfine powders as ingredients in their sunscreens. Zinc oxide is the primary active ingredient in many baby care products and thus has a very long history of safe use and is not associated with any allergic reactions. Because of this, physical sunscreens, like zinc oxide, are ideal for beach products and for products such as moisturizers and make up that are used every day and need to be as gentle as possible. Most of the organic sunscreens block only UVB. Titanium dioxide blocks some UVA and Zinc oxide blocks more UVR than any other single ingredient. When buying a sunscreen you should get at least an SPF 15 and preferably one that contains zinc oxide. At a minimum, make sure it says "Broad Spectrum".

You should apply the sunscreen about 20 minutes before going out. This gives the sunscreen time to "set up" on your skin so that it can do its job. An SPF 2 blocks about 50% of the UVR. An SPF 10 gets about 85%. An SPF 15 stops about 95% and an SPF 30 stops about 97%. That is why most health professionals agree that an SPF 15 is enough. This all assumes that the sunscreen is applied correctly. When the SPF test is done the testing lab uses an amount of sunscreen representative of 1 ounce per each full body (adult) application. This means that the average 4 ounce tube would last an adult 4 applications at the beach. If you stayed on the beach 4 hours and applied the sunscreen every 2 hours then a tube would last only 2 days (4 applications). Virtually nobody uses this much sunscreen which means more often than not, the sunscreens are being under-applied and people are not receiving the protection they think they are. Some people try to get around this by using a higher SPF but less of it. For instance, it's appealing to think that if you use a little bit of SPF 30 its really like using an SPF 15. Unfortunately, it doesn't work that way. There is no good way to predict the SPF of an improperly applied sunscreen so - bottom line - use at least an SPF 15 and use it correctly!