THE AUSTIN DERMATOLOGIST INSIGHT ON SUNSCREEN

There has been some mistaken belief that sunscreens in general are bad and should never be used on anybody, and others feel that sunscreen should be used at all times by every single person. Both may be incorrect.

The original sunscreens were PABA-based. They were actually very good because of PABA's inherent "adherence" or binding to the skin. It got into the skin and stayed there. It didn't float off or sweat off. Unfortunately, some people were allergic and all you now see is "PABA-free." Frankly, if I could have PABA back, I would.

What follows will be my thoughts on sunscreens in general and how to use them properly.

SPF NUMBERS - The SPF means sun protection factor. This is based on your Fitzpatrick skin type (see last page) and has to do with how long you can stay in the sun with the sunscreen vs without. The endpoint is when you begin to burn. Technically, an SPF 15 means that you can stay in the sun 15 times longer before you burn than you could have without it. This is a bit deceiving since they are looking at burn as the endpoint. A burn is from the UVB rays and a tan is from the UVA rays. More about this later. An SPF 15 if used frequently and properly can be enough sunscreen for most people, and a typical SPF 15 will block about 90% of these rays. Doubling it to an SPF 30 only blocks up to about 93%. In other words, doubling the SPF did not double the protection. One could still argue, why not get all of the protection you can, and if there is no reason not to, then perhaps the highest SPF is always preferable.

UVA/UVB/UVC - These refer to wavelengths of light. Visible light is all of the light that bounces off all of the objects that allow you to see them. This wavelength is from 400 to 700 nanometers. A nanometer is a billionth of a meter, and that distance is from the crest of one wave to the crest of another. For whatever reason, God wanted our eyes to be able to see within this wave range. Anything above it is infrared (heat) and anything below it is ultraviolet which we will talk about later. UV radiation from 245 to 290 nanometers is absorbed maximally by the DNA of your cells, thus implicating UVB as the primary mutagen. UVA causes damages to DNA differently by the generation of ROS (reactive oxygen species). These are oxygen-based free radicals which damage cellular DNA as well as lipids and proteins in your cells. There is ongoing research to see if this can be reversed by either the oral ingestion of certain medications and foods or in their topical application. I wouldn't trust these yet - the research is not in. One thing NOT shown to prevent such damage is vitamin E. It simply doesn't work whether used orally or topically! High doses of vitamin A otherwise known as retinoids (even Accutane) can mitigate some of this damage but in those doses there are other more serious potential side effects including elevated blood fat levels (cholesterol and triglycerides), bone damage, and liver damage. If you take excess vitamin A or beta carotene on your own from one of the health food stores...beware! Excess levels of Vitamin A are deadly. Do not listen to these people and do not trust that high doses of beta carotene (which they may tell you is safe vs vitamin A) is a good idea. The dose that may protect you may be indeed the dose that may hurt or kill you. In fact, smokers who prophylactically tried higher doses of Vitamin A had MORE lung cancers, not less!

Ultraviolet C (UVC) is below 280nm. It is of no consequence to this discussion. Ultraviolet B (UVB) is 280 to 320 nm and Ultraviolet A (UVA) is 320 to 400 nm.

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