Professional Opinion: What spots do we miss when applying sunscreen?

rdamgen@beaufortgazette.comApril 14, 2014 

Paul Brewer, a board-certified dermatologist in Beaufort

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This week, Paul Brewer, a board-certified dermatologist in Beaufort, discusses spots you commonly miss when applying sunscreen and whether a base tan really protects your skin.

Question. When it comes to sunscreen application, what is the most-missed area on your body? Where do you see the most instances of skin cancer? If I have a base tan, can I wear a lower SPF?

Answer. For women, the most missed areas would include the lips, the tops of the feet and the back of the neck. For men, the most commonly missed areas are everywhere. Males are in heavy denial about sunscreen and the need to apply it.

We advise our patients to use sunscreen that has an SPF of 30 or higher, is water resistant and provides broad spectrum coverage. Our favorite sunscreens include physical blocking agents such as micronized zinc oxide and titanium dioxide. These agents work immediately and give the best protection against UVA and UVB rays.

Patients often ask about zinc oxide and titanium dioxide being turned into nano particles. There is no conclusive evidence that nano particles enter the skin, nor do they have any harmful effect. The benefit of nano particles is that these ingredients do not leave a white residue on the skin, which would make you look like Casper the friendly ghost.

We also encourage our patients to use enough sunscreen. Recent studies have revealed that most adults put on approximately half the amount of sunscreen that needs to be applied. Therefore if you are applying a sunscreen with an SPF of 30, you are actually only achieving an SPF of 15 by applying half as much as you should. As a rule the average adult should apply 30 grams or 1 ounce of sunscreen for complete protection. Sunscreen should be reapplied at least every 2 hours to remain protected or immediately after swimming or excessive sweating.

Skin cancer is most commonly found on the face, backs of hands and the scalp. For men, melanoma is most commonly found on the upper back and the upper extremities. For women, melanoma is most commonly found on the lower extremities and on the face. If you detect a new lesion on these areas or a spot anywhere on your body that is not healing, bleeding or is a painful, you should see your dermatologist for an examination. Any new moles or changes to existing moles should be brought to the attention of a dermatologist to rule out melanoma. Women in their 20s and 30s should be on the lookout for changing moles; there has been a significant rise in the diagnosis of melanoma in this age group due to indoor tanning.

When someone has a base tan, that confers an SPF of 4 to 6 at best. But, SPF isn't additive. If you applied an SPF of 15 and you had a base tan, you wouldn't have an SPF of 21. You'd have an SPF of 15. Another scenario would be if your makeup has an SPF of 15 and you also applied sunscreen with an SPF of 15 -- your total protection is still SPF 15, not 30.

Follow reporter Rachel Damgen on Twitter at twitter.com/IPBG_Rachel.

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