Sun damage: the basics

The sun emits harmful ultraviolet (UV) radiation, which can result in skin damage ranging from freckling to cancers. There are essentially three types of UV radiation: UVA and UVB, which penetrate the ozone layer, and UVC, which is the most harmful but for now is absorbed by the ozone layer so does not reach the earth's surface. UV radiation causes damage to the epidermis (the outer layer of the skin) through its effects on connective tissue, DNA, and increased production of free radicals. Free radicals are oxygen-containing molecules that are normally produced and cleared by the body, but are damaging in excessive amounts.

UVA radiation is responsible for photoaging, which is skin damage due to excessive sun exposure. Photoaging describes damage such as premature wrinkling, dry rough leathery skin, freckles, and discolorations (solar lentigines, or age spots) on the face, back of hands, arms, chest, and upper back.

Both UVA and UVB radiation contribute to the risk of developing actinic keratosis (a precancerous condition) and skin cancer. Cancers develop due to damaged DNA and, if not detected early, can result in disfigurement and even death.

Tanning and sunburns are two visible signs of sun damage. Many people think that they are not serious and are part of enjoying the season. However, the damage accumulates over time and results in photoaging or skin cancers. It is well known that fair-skinned individuals have less skin pigmentation and are at a higher risk of sun damage. However, even darker-skinned people are not exempt from developing skin cancers and should also protect their skin from the sun's harmful rays.

So the general rule is that everybody needs to use some form of sun protection! It is recommended that you use a broad-spectrum sunscreen - one that protects you from UVA and UVB radiation - and abide by the following guidelines:

  • Avoid the sun between 10 a.m. and 3 p.m. (11 a.m. and 4 p.m. daylight saving time).
  • Wear wide-brimmed hats, long-sleeved shirts, and long pants.
  • Consider wearing sun-protective clothing. Unlike sunscreen, this form of sun protection does not wear off. It is highly protective against UV radiation.
  • Choose sunscreens that have a sun protection factor (SPF) of at least 15 and that have both UVA and UVB coverage.
  • Apply sunscreen at least 15 to 30 minutes before going out (follow the instructions on the label). Reapply every 2 to 3 hours - more often if you are swimming or perspiring.
  • Avoid tanning beds.

SPF stands for sun protection factor. The SPF rates a product's ability to protect an average user's skin from sunburn when the product is used properly. When used properly, an SPF 15 sunscreen protects the skin from 93% of UVB radiation; SPF 30 and SPF 45 sunscreens provide more than 96% protection from UVB.

Even though they block the harmful UV rays, sunscreens do wear off, so it is very important to reapply them frequently. Make sure you use the correct amount of sunscreen, too. Adults should use about one ounce of sunscreen to cover their entire body. Generally, an 8-ounce bottle should last a family of four less than a week.

The contents of this health site are for informational purposes only. Always seek the advice of your physician or other qualified healthcare provider regarding any questions you may have about a medical condition.

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