Too Much Sun

By Dr. Mark Wise

"The sun did it!!!"

This cheery advertising slogan used to refer to that subtle blond bleaching of the hair so popular back in the Troy Donahue (back in the 50's) days. Now, when we give credit to the sun, it's more likely to be because of premature aging of the skin, photosensitivity reactions and skin cancer. A tan is no longer considered a sign of good health. Rather, it represents skin injury.

THE ABC's

Let's look at the ABC's of the suns rays, that is, the different types of ultraviolet radiation to which we are exposed.

UVA: This is long-wave radiation between 320 and 400 nanometres. It is responsible for most photosensitivity reactions, and also contributes to chronic skin damage and sunburn. It penetrates deeper into our skin than UVB radiation. Its level is relatively constant during daylight hours.

UVB: The midrange of ultraviolet radiation (290 to 320 nm) is the major cause of sunburn and chronic skin injury, including aging and skin cancer. It is most intense between 11 am and 4 pm. It is able to penetrate through 1 metre of water, and is reflected 17% by water, 50% by sand, and up to 80% by snow.

UVC: This wavelength of radiation does not reach the earth's surface, as it is blocked by the ozone layer. However it is found in artificial light sources such as tanning beds. It may cause erythema, or sunburn.

Certain people may be more susceptible to the effects of the sun. This will include those with fair skin, freckles or numerous moles, people who tend to burn easily or tan minimally, those taking certain medications which cause photosensitivity, and anyone with a family history of skin cancer. Most of our sun exposure occurs by the time we are 20 years old, so protection is particularly important in children.

Sun damage may be avoided by:

•Minimizing exposure to the sun, especially between the hours of 11 am to 4 pm

•Wearing protective clothing, especially a hat

•Using sunscreens or sunblocks

SUNSCREENS and SUNBLOCKS

Sunscreen work by "absorbing" the sun's rays so that they do not hit the skin. Their relative effectiveness is measured by the SPF, or Sun Protection Factor. The higher the SPF, the more, or longer the protection you receive. Theoretically, an SPF will allow you to remain in the sun 15 times longer without burning than if you didn't apply it. These numbers may be an overestimate. In addition, many sun worshippers do not apply their sunscreen properly or adequately.

The various components of your sunscreen may include PABA, Padimate, benzophenones, cinnamates, salicylates. Parsol should be a component of any sunscreen, as it is the only chemical which blocks UVA.

True sunblocks, which may be less cosmetically pleasing (or perhaps more), include titanium dioxide and zinc oxide. They are particularly useful on the more exposed body parts, such as ears and noses.

When choosing a sunscreen, consider your own sensitivity to the sun. Everyone should use a sunscreen with an SPF of at least 15. Those who are more susceptible should use something stronger. If you are going to be spending time in the water, or sweating, choose a sunscreen that is water resistant, or even better, waterproof. Sunscreen should be applied to the skin at least 20 minutes before exposure to the sun.

There are a lot of excellent products on the market. Here are the names of some of the good ones … Bain de Soleil, Presun, Ombrelle. Read the small print to see which one is most appropriate for your skin and your type of exposure.

I must admit, I've had more than my share of sunburns over the years. Mexico, Guatemala and India come to mind. In addition to a painful burn, you may feel sick as a dog! So cover up, relax in the shade (that's what the local people do), and use lots of your sunscreen.

© Copyright 2000 Dr. Mark Wise

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