Ask SAM

By: Ask Sam | Winston-Salem Journal
Published: June 22, 2009

Q. This is a serious question for which no one seems to know the answer: If you put on SPF 15 sunscreen, then put SPF 30 over it, do you now have SPF 15, 22.5 (the average of the two), 30 or 45? -- B.B.

A.You would end up with SPF 30.

"Unfortunately, layering sunscreens does not give added SPF protection" writes Dr. Jeffrey Benabio, who has a dermatology blog at Thedermblog.com. "The SPF you end up with is only the SPF of the highest sunscreen that you applied."

Since SPF is a hot topic for the summertime, SAM wanted to explain more about sunscreen.

SPF stands for sun protection factor, and indicates how well the product can deflect the sun's ultraviolet B rays -- the ones that cause sunburn. A higher number indicates that you should be able to spend longer in the sun without burning.

Another type of solar radiation, ultraviolet A, is implicated in skin aging. But a product's SPF rating tells nothing about how well it deflects UVA rays. Both UVA and UVB rays are implicated in skin cancer. "Broad-spectrum" sunscreens protect against both types of rays, but currently there is no scale to indicate a sunscreen's effectiveness against UVA.

So SPF doesn't tell the whole story about sun protection. Also consider that how much sunscreen is applied affects how effective it is. A rule of thumb is that people need to use about an ounce of sunscreen -- enough to fill a shot glass -- to cover themselves completely. If you apply less than recommended, you won't get the full SPF on the label.

Bottom line, from the American Academy of Dermatologists: "Dermatologists strongly recommend using a broad-spectrum (UVA and UVB protection) sunscreen with an SPF of 15 or greater year-round for all skin types. This will help protect against sunburn, premature aging (e.g., age spots and wrinkles) and skin cancer."

For the best protection, be sure to apply sunscreen liberally and thoroughly about 20 minutes before you go out in the sun. You need to reapply every couple of hours, or after swimming, sweating or toweling off. Whenever possible, wear protective clothing such as hats and long sleeves, and seek the shade and stay out of the sun as much as possible -- especially during the hours when the sun is strongest, from 10 a.m. to 4 p.m.

A good source for more information about sunscreens is the Skin Cancer Foundation, which has much information at www.skincancer.org/Sunscreens-Explained.html.

Q. While visiting the Outer Banks last week I noticed several license plates that started with OBX and followed by five digits. For example OBX12345. I know that normal license plates in North Carolina have three letters, a dash and then four numbers. Are these OBX12345 plates regular plates for those living in the Outer Banks, or are they specialized plates that require an extra fee like the collegiate or special interest plates? -- P.K.

A. The license plates with OBX followed by five digits are standard license plates. Kay Hatcher, a Special License Plate Unit supervisor with the NCDOT, said they do not require a special fee in addition to license fee. The license plates are issued from the Manteo License Tag Office only.

Follow-up

After SAM wrote about Billy "Crash" Craddock, a country-music star and Greensboro native, several fans let us know that Craddock is scheduled to perform at the Old Threshers Reunion in Denton at 3 and 8 p.m. July 4. More information about the Threshers Reunion is available at www.threshers.com. More information about Craddock, including information about coming performances, is available at www.billycrashcraddock.net.

E-mail: AskSAM@wsjournal.com.

Online: www.journalnow.com/asksam.

Write: Ask SAM, P.O. Box 3159, Winston-Salem, NC 27102.