Student Health Center

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Travel Kit

Are you adequately supplied with sunscreen?

There are two basic types of ultraviolet rays that reach the earth's surface from the sun--UVA and UVB. UVB rays are responsible for sunburn and play the greatest role in causing skin cancer.
They affect the outer layer of skin, are filtered by glass and the intensity varies depending on time of day and year. UVA rays also contribute to the development of skin cancer, penetrate more deeply into the skin and play a greater role in premature aging changes, including wrinkles. They are also responsible for photosensitivity reactions, such as those caused by some medications. UVA rays are not filtered by glass, make up a much greater proportion of sunlight and have more constant intensity. They can penetrate cloud cover, pollution and about 3 feet of water.
A sunscreen's effectiveness in protecting the skin is expressed as SPF (sun protective factor). It is the measure of the ability of the product to block UVB rays. If you use a sunscreen having a SPF of 5, then theoretically you can stay outside 5 times longer before getting a sunburn than you could without the sunscreen.  A SPF 15 sunscreen blocks 92% of UVB rays, while a SPF 30 blocks 96% of the rays.  It is estimated that most people only apply 20-50% of the amount used to determine the products SPF, so you are probably getting much less protection than you think, i.e. your SPF may be 15, but you are really only going to get a photoprotective power of 3.

There is no measure of UVA protection, so you should look for products that contain avobenzone (Parsol 1789), benzophenones, titanium dioxide or zinc oxide. These chemicals have UVA blocking abilities. Considerable exposure to UVA can occur even in the shade. It is particularly important to block UVA  if you are outdoors for long periods on a daily basis, or are using a photosensitizing medication. Tanning salons use UVA rays.

If you wear sunscreen that only blocks the UVB rays you can actually increase your chance of developing skin cancer because by blocking the UVB rays you can prolong your sun exposure and accumulate more UVA exposure. Many studies show that the probability of sunburn/sun damage actually increases for those that use sunscreen because they overestimate the time and thoroughness of the protection.

Want more info?       Read on.....            

To get the most from your sunscreen you want to:

• Apply sunscreen every day--not just when it is sunny
• Apply ~30 minutes before going outdoors to dry skin
• Apply it in adequate amounts--a minimum of 1 ounce is needed for adequate total body coverage (about a handful).
• Water-resistant sunscreens protect skin for ~ 40 minutes of water exposure, whereas water-proof protect for ~ 80 minutes.
• Gels work well for oily or sweaty skin, lotions for dry skin, sprays for the total body and sticks for ears, lips and around eyes.

• All sunshine is not created equal:
  
• Maximum exposure occurs between 10am and 4pm.
• Intensity of radiation is much greater in the summer
  
• UV radiation increases 4% per 1,000 feet of elevation.
• Reflected radiation is just as damaging as direct, and water reflects up to 100% of radiation, snow reflects up to 85% and sand or concrete reflect 25 % of radiation.

• A 4 inch brimmed hat reduces sun exposure by 70% to your head face, and neck.
• A white, dry cotton shirt  provides an SPF of ~8.  The SPF increases if the fabric is dyed or thicker.
• Sunglasses that block at least 98% of UVA and UVB should be worn. UVB radiation is linked to the formation of cataracts. 
  The darkness of the lenses does not correlate with the UV protection.