This document discusses sunscreen and sun protection. It explains that UV rays from the sun can damage skin and potentially cause skin cancer. It recommends using sunscreen with at least SPF 15 and reapplying every two hours. Higher SPF sunscreens do not provide significantly more protection above SPF 50. Physical (mineral) sunscreens offer protection immediately while chemical sunscreens take 15-30 minutes to be effective. Proper application, covering all exposed skin and reapplying is important to receive full protection from sunscreen.

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SUNSCREEN
Laura Bishop, M.D.
University of Louisville Pediatrics
July 2013

2. +
UV Light
• UVC
• Most damaging
• Little makes it
through
atmosphere
• UVB
• Still damaging
• Most common
cause of skin
cancer
• UVA
• Least damaging
• Causes many of
sun’s aging effects

3. +
Sun Avoidance
 This is especially important for
infants.
 Avoid peak sun hours
o 10 a.m. to 2 p.m.
 Coverage
o Select clothing + hats that cover
frequently burned areas
o Use sunglasses with UV protection
o Use shade to your benefit
AVOID PEAK
SUNLIGHT
HOURS
PROTECTIVE
CLOTHING, S
UNGLASSES
& HATS
SEEK OUT
SHADE
SUNSCREEN

4. +
SPF
 SPF = sun protection factor against UVB
rays
 UVB rays burn and cause cancer
 UVA damages skin long-term
 SPF is determined by testing 20 sun-
sensitive people and measuring the amount
of UV rays (in time) it takes to turn skin red
without sunscreen. Then it is repeated with
sunscreen and the average burn time with
sunscreen is divided by the average burn
time without sunscreen number.
 Calculate how long a sunscreen will protect
you:
 Mins to burn without X SPF number = max sun
exposure time.

5. +
Sunscreen
SPF
% UV
absorbed
2 50
4 70
8 87.5
15 93.3
30 96.7
50 98
 The previous formula only works if you use the
proper amount of sunscreen
 the average person only uses half as much as
recommended amount.
 A higher SPF does not mean an exponential
increase in UVB absorption.
 FDA has proposed a cap on SPF with anything
above 50 reading 50+ to prevent public
perception that SPF 80 is significantly more
protective.

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Sunscreen: What to Buy
 Type of Sunscreen
 Physical (inorganic)
 previously called sunblock, often contains zinc
 Newer formulations are invisible
 Chemical – standard sunscreen
 SPF
o At least SPF 15
o But not much benefit over SPF 50
 Broad Spectrum
 Waterproof
o DOES NOT EXIST!
o Water resistant lasts either 40 or 80 minutes
without reapplication.

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Sunscreen: 2011 FDA Changes
• Should include
UVA
information:
labeled broad
spectrum.
• Can no longer
be labeled:
waterproof, swe
atproof or as a
sunblock.
• Duration (40 or
80 minutes) of
water
resistance
should be clear.

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Sunscreen: How to apply
 All types of sunscreen should be applied
15-30 minutes prior to outdoor activity.
 Physical sunscreens are immediately
effective.
 Throw it away if past expiration date or
over two years old.
 Apply generously.
 Experts recommend half a teaspoon each
for the head, neck, and each arm and a
teaspoon each for the chest area, the back,
and each leg.
 Or, a one-ounce shot glass full for an
average-sized adult.
 Reapply every two hours or per water
exposure directions on bottle.

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Don’t miss a spot!
 Most commonly missed spots:
 Creases of elbows and knees
 Feet
 Hands (these are exposed to the sun daily!)
 Ears and behind ears
 Scalp and neck
 Don’t forget lip protection!

10. +
Resources
 http://health.howstuffworks.com/skin-care/beauty/sun-care/spf.htm
 http://healthguide.howstuffworks.com/melanoma-and-other-skin-
cancers-in-depth5.htm
 FDA, “Understanding Sunscreen.”
http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsi
ngMedicineSafely/UnderstandingOver-the-
CounterMedicines/ucm258468.htm
 http://www.aap.org/advocacy/releases/summertips.cfm
http://www.healthychildren.org/English/news/Pages/Summer-Safety-
Tips-Sun-and-Water-Safety.aspx