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Protect your skin from sun damage

Published July 2, 2016
• Reviewed by a UI Health Care Provider
on April 1, 2018

SPF and UV rays

When comparing products that protect the skin from the harmful effects of UVB rays, the term sun protection factor (SPF) is often used. For example, if you used a sunscreen having a sun protection factor of 5, then theoretically you could stay outside in the sunlight five times longer before getting a sunburn compared to the time required to get a sunburn without using the sunscreen. The SPF relates only to the ability of a sunscreen to block sunburning UVB rays. The SPF number does not relate to the ability of a sunscreen to block UVA rays.

Avoid direct sun exposure

You should avoid direct sun exposure and artificial tanning devices as much as possible. You should be especially careful to avoid midday sun exposure. Midday summer sunlight has the greatest concentration and intensity of UVB and UVA rays.

A useful rule of thumb is if your shadow is longer than you are tall there is less danger from the damaging effects of UV rays. This generally applies before 10 a.m. and later-than 4 p.m. in the spring and summer months. It is also a good idea to check the UV Index each day and dress accordingly. The UV Index is a prediction of the sun’s UV ray strength on any given day at noon in a particular geographic region. The local daily UV Index is usually available online.

  • Harmful UV rays also can reflect off water and light-colored surfaces (e.g. concrete, sand, and snow). This can double the amount of UVB rays that strike your skin.
  • UV rays also reach below the surface of water—three feet of water blocks only 20 percent of UV rays.
  • Sunscreen should be used even on cloudy days when up to 80 percent of UV rays can still reach the earth’s surface.
  • Repeated small exposures to UV rays may account for 80 percent of total exposure over a lifetime.
  • Daily use of a sunscreen is very important since intermittent application is much less protective.
  • You should wear lightweight, tightly-woven clothing and broad brimmed hats.

Cover up with hats and clothing

A hat brim of 4 inches or greater is recommended, and you should make certain the top and brim of a straw hat have sun-proof liners in place. Small-brim hats (less than 1 inch) provide a sun protection factor of 1.5 for the nose and minimal protection for the chin. Broadbrim hats (greater than 3 inches) provide a SPF of 3 for the cheek, SPF 7 for the nose, SPF 5 for the neck, and SPF 2 for the chin. There are lightweight plastic hats that are commercially available and designed specifically to provide a physical block to UV radiation.

Typical summer shirt fabrics only offer SPF of 6.5. Weave tightness is the most important factor in sun protection of fabrics followed by the fabric type. Cotton and polyester/cotton blends offer comparable protection. When stretched, Lycra fabric is significantly less effective than when it is lax. Darker color fabrics provide greater protection from UV rays than do lighter color fabrics. It is also important to note that fabrics are significantly less photo-protective when wet. Several clothing lines offering maximized UV protection (SPF 30) are available. Such sun-protective specialty clothing is also marketed for fishing and boating. 

Protection from other UV sources

For maximal UV protection, acrylic diffusion shields should be placed over bare fluorescent light tubes/bulbs at home and at work to block the small amount of UV irradiation that can leak from such light sources (UVA greater than UVB). In addition, UV blocking plastic adhesive films can be applied to home and automobile windows. A number of companies offer UV light blocking films or plastic shields that can be applied to home and automobile windows. This is important because whereas window and car glass material may offer some shielding against UVB rays, they are transparent for UVA rays.