SunScreens and SunBlocks
Carol Beard, RN, BS.N., Ann C. Slocum, Ph.D., Joanne Schultink, M.S.
Human Environment and Design Department, Michigan State University


Areas not covered by clothing require a sun protective product to provide a barrier from the sun, although these products are not considered as effective as clothing for reducing UV exposure (Reinert, 1997).  Two kinds of sun protective products are available.  One is a sun block, which as the name suggests, provides a "physical block" that functions by reflecting rays.  Sun blocks contain minerals which "bounce back" light to stop the UV rays from hitting your skin.  The other type of sun protective product is a chemical sunscreen.  Sunscreens work by absorbinga minimal amount of the UV rays and filtering them into a harmless infrared wavelength.  If you have sensitive skin, the reflective sun blocks can be better, since the chemicals in high-factor sunscreens can irritate the skin when they interact with the sun.  What many people might consider a heat rash may actually be an allergic reaction to their sunscreen (Maier, 1999).

What SPF numbers tell us
Sun blocks and sunscreens are labeled according to their sun protection factor or SPF.  The SPF tells you approximately how long you can stay in the sun before you will get a sunburn. For instance, if it typically takes you 20 minutes in the sun to burn without sunscreen, an SPF 15 sunscreen lets you stay in the sun for about five hours without burning.  To find approximately how long you can stay out, multiply the amount of time it takes for the skin to redden without sun screen, times the SPF number (in this example, 20 minutes x 15 (SPF ) = 300 minutes, or five hours).  Numbers on sun protective products can be misleading.  Once you get above SPF 15, the numbers aren't truly representative of how much more powerful they are, that is, higher SPF numbers are only a little more powerful.  Higher numbers can lull the consumer into a false sense of security, therefore we recommend that you calculate your time in the sun conservatively, using 15 (SPF) as a basis for calculation.  Once you have reached your limit for time in the sun based on this calculation, you need to get out of the sun (Maier, 1999; Acerrano, 1996).

Using Sun Protective Products
Application.     During your time in the sun, reapplication of the sun protective product is important.  Preferably it should be reapplied every one-two hours due to perspiration, swimming and toweling off, etc.  Reapplication is for the purpose of maintaining protection within the amount of time calculated based on the SPF (5 hours in the example above).  Reapplication does not extend the time you should stay out!  After that length of time, your sunscreen will cease to be effective (Maier,1999).

It is also key to apply it liberally.  An ounce is needed to cover the whole adult body, and you should rub it gently in and not just slap it on top of the skin.  This helps the active ingredients penetrate to the layer where they do their work.  The sun protective products should also be applied 20-30 minutes prior to going outside, as it needs time to take effect (Boyer, 1996; Brink, 1996).  "Expiration dates vary but should be on the bottle.  If not, ask your pharmacist.  Any sunscreen older than two years most likely has lost some of its effectiveness" (DiGiovanna, 1998).

Daily Use.    Since nearly 70 percent of all UV exposure stems from daily activities such as walking, jogging, driving (UV rays pass through glass), it is important to wear a sunscreen product with a SPF of 15 or more each day.  This is especially important when you are around reflective surfaces, like water or snow that will reflect the sun's rays, increasing exposure.  It is also important to use a protective lip sunscreen--the lower lip is very vulnerable to non-melanoma skin cancer.  "Lips require extra sun protection because they're devoid of melanin, the skin's natural defense against the sun.  Apply sun protective products to your lips when you do the rest of your face, then carry lip protector with sunscreen to apply during the day" (Boyer, 1996).

Sun Protection for All
While people who are fair-skinned have 20 times more the risk of getting skin cancer than dark skinned people, research shows that African Americans also need to take sun protective actions such as using sunscreen or sun block and avoiding intense sunlight.  Important indicators of the need for sun protection for dark skinned people are skin sensitivity and skin reaction after a short period and after a long period of sun exposure.  In general, all populations need to practice sun protective behaviors (Hall, Rogers, 1999).

If we adopt the Australian slogan "Slip, Slap, Slop" --slip on a T-shirt, slap on a hat, and slop on some sunscreen we can consistently reduce UV exposure (Perry, 1996).  We need a lifestyle of avoiding over exposure, but when in the sun, a lifestyle of maximum sun protective behaviors.

Fake Tans
A fake tan achieved by applying a coloring material to the skin is safe in that it doesn't involve exposure to ultraviolet light.  However, it is important to remember that fake tan offers absolutely no protection to UV rays because the tan isn't achieved through the production of melanin, the skin's natural sunscreen.  Therefore, you are no more resistant to sun damage than you would normally be without a tan, and you need to wear your sun protective products when you go outdoors (Maier,1999).

Return to SunWise Menu
                Go to other detailed information

introduction protective clothing tanning beds
sunglasses references

Copyright (c)1999-2000 Michigan State University. All rights reserved.

Disclaimer, Indicia , & Project Credits