Sunscreen Smarts

Ronda Miller-Ernest, a pediatric nurse practitioner with Intermountain Pediatrics in Salt Lake, answers questions about sunscreen.

What is the difference between chemical sunscreens and barrier sunscreens?

Chemical sunscreens contain ingredients that act as filters and reduce the ultraviolet radiation penetration to the skin. These ingredients must be absorbed into the skin so that is why these chemical sunscreens need to be applied 30 minutes before sun exposure!

Barrier sunscreens are often referred to as sunblocks, but not always. Barrier sunscreens act as a sun block by reflecting and scattering the ultraviolet light away from the skin. They stay on the surface of the skin and are not absorbed. The most common products generally used in barrier sunscreens are Zinc Oxide and Titanium dioxide.

What does SPF stand for?

SPF stands for sun protection factor. SPF numbers indicate the length of time one can spend in the sun without risk of burning. For example a person who is very fair skinned who normally may burn in 20 minutes may tolerate 15 times longer (300 minutes) with a SPF sunscreen of 30. Or a person who may experience a burn within 10 minutes can be protected up to 150 minutes with a SPF sunscreen of 15.However that doesn’t necessarily mean they don’t need to re-apply sunscreen for 5 hours, it still follows the every 2 hour rule of applying sunscreen. SPF of 15 theoretically filters 92% of UVR (ultra violet radiation) and SPF of 30 filters 97% UVR. A young infant or child or people who are faired skin would obviously benefit from a sunscreen with at least a SPF of 30. Statistically people only apply 1/3 of the recommended amount of sunscreen, so theoretically if you only apply 1/3rd of the required amount of a sunscreen with a SPF of 30 you are really only getting a SPF protection of 10.

How much sunscreen is enough?

Approximate amounts per age would be:

3 teaspoons for an infant/toddler.

6 teaspoons for an 8 year old. (one ounce) And then adjust accordingly.

Do you still need to re-apply sunscreen if it says “waterproof” or has “all day protection”?

Yes, don’t be fooled by those labels. Stick with the “apply every 2 hours” rule.

What are the guidelines for sunscreen and babies?

It is recommended by both the American Academy of Pediatrics and the American Academy of Dermatology that Infants younger than 6 months should never be exposed to direct sunlight. The thought is that not that the sunscreen is harmful to use on an infant under six months but that direct sunlight is harmful to such delicate skin and therefore protective clothing and complete shade should be the protection of choice!

Does sunscreen block the absorption of vitamin D?

The amount of UV exposure to synthesize vitamin D depends on so many other variables such as amount of skin pigmentation, body mass, the season, cloud cover, amount of skin exposed and protection such as clothing and amount of sunscreen, so it is difficult to assess how much Vitamin D would be absorbed without use of sunscreen. The risks of sun exposure outweigh the benefits of Vitamin D absorption therefore if someone is deficient in Vitamin D a supplement is recommended over sun exposure.

Ronda Miller-Ernest is a pediatric nurse practitioner at Intermountain Pediatrics in Salt Lake City.

508 East South Temple, Suite 310


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