II. Technique
- Use Sunscreen with SPF of 15 or higher
- SPF 15-30 is typically sufficient protection for most patients
- SPF 15 blocks 93% of UVB
- SPF 30 blocks 97% of UVB
- SPF 50 may be considered for patients at high risk of Skin Cancer
- SPF 50 blocks 98% of UVB
- SPF above 50 is unlikely to provide additional benefit
- No added protection or prolonged duration of activity
- SPF 15-30 is typically sufficient protection for most patients
- Use Sunscreen that blocks UVA and UVB
- Most current Sunscreens block UVB
- SPF rating does not apply to UVA
- "Broad spectrum" denotes protection for both UVA and UVB
- Zinc Oxide
- Titanium Dioxide
- Drometrizole trisiloxane (Mexoryl)
- Shake Sunscreen well before using
- Darker skinned patients should use Sunscreen
- Although high Melanin concentrations reduce UV penetration, it does not eliminate UV-induced Skin Cancer
- Sheer Sunscreens and dark-tint Sunscreens are available which may be more cosmetically acceptable for patients
- Avoid spraying Sunscreen on face
- Risk of inhalation
- Spray Sunscreen onto hands and then apply to face
- Wear Sunscreen on all outdoor daylight exposures
- Cloudy days: 80% UV radiation penetrates clouds
- Swimming: 50% UV radiation penetrates water
- High altitude (UVB increases 8-10% per 1000 feet)
- Exposure to snow or water (reflective surface)
- Apply 2-3 tablespoons (1 ounce or shot glass size) of Sunscreen for whole body
- Do not forget around eyes, ears and mouth
- Apply to scalp if bald or hair thinning
- Apply Sunscreen 15 minutes before exposure and then every 2 hours (regardless of SPF)
- Reapply Sunscreen every 1 hour when sweaty or wet
- Water resistant (or water proof) sun screens require the same frequent replacement when wet
- Protect babies and children well from Sun Exposure
- Keep infants under 6 months in shade or covered
- If unable to keep out of sunlight, use a physical Sunscreen
- Apply Zinc Oxide or Titanium Dioxide containing Sunscreen for maximal protection
- Replace old Sunscreens
- Changed colors
- Significantly past their expiration dates (esp. if exposed to Temperature extremes)
- Protective Clothing
- Covering skin with Ultraviolet Protection Factor (UPF) Clothing also offers sun protection
III. Physiology
- Sun Protection Factor (SPF) ratio
- Time to produce slight erythema on suncreened skin to
- Time to produce same erythema without Sunscreen
- SPF Interpretation
- "Broad spectrum" denotes protection for both UVA and UVB
- SPF gives no information on Ultraviolet A protection
- SPF reflects protection from UVB Light
- SPF 15 blocks 93% of UVB
- SPF 30 blocks 97% of UVB
- SPF 50 blocks 98% of UVB
IV. Preparations: Chemical or Organic Sunscreens
- Avobenzone (Parsol 1789)
- Absorbs both short and long wavelength Ultraviolet A
- Does not absorb Ultraviolet B (UVB)
- May be degraded by sunlight exposure
- Menthyl Anthranilate
- Absorbs shorter wave length Ultraviolet A
- Oxybenzone
- Absorbs shorter wave length Ultraviolet A
- Banned in Hawaii as of 2021 due to adverse effects to ocean wildlife (coral bleaching, reproduction)
- Octinoxate
- Absorbs UVB
- Banned in Hawaii as of 2021 due to adverse effects to ocean wildlife (coral bleaching, reproduction)
V. Preparations: Physical, Mineral or Inorganic opaque compounds (scatter light)
- Types
- Titanium Dioxide
- Zinc Oxide
- Nanoparticles
- All physical Sunscreens are classified as nanoparticle, even if they are advertised as "non-nano"
- None of the physical Sunscreens are absorbed through the skin regardless of size (nano or "non-nano")
- Nanoparticle Sunscreens are typically easier to apply
- Nanoparticle size may have environmental impact, but the effects are not currently known
VI. Efficacy
- Reduced with wind, heat, humidity, and altitude
- Reduced with poor or inadequate application
- Most people do not apply enough Sunscreen
- Multiple layers required to reach listed SPF
- Reduces Incidence of Actinic Keratoses
- Decreases photoaging
VII. Safety
- Regular Sunscreen use does NOT result in Vitamin D Deficiency in most patients
- However, Vitamin D may be reduced 30% in those who regularly use Sunscreen and protective clothing
- Passeron (2019) Br J Dermatol 181(5):916-31 +PMID: 31069788 [PubMed]
- Oxybenzone, Zinc Oxide and Titanium Dioxide are safe on skin
- Reef safe labeling
- Some products, such as Oxybenzone, have been associated with coral reaf bleaching
- Some regions (e.g. Hawaii) have banned Oxybenzone, Octinoxate, Avobenzone, Octocrylene
- Physical Sunscreens (Zinc Oxide, Titanium Dioxide) are very effective and are considered "reef safe"
- However "reef safe" has no standard definition
- Use of effective Sunscreen is paramount in the prevention of Skin Cancer (esp. in reef regions)
- Absorption
- None of the physical Sunscreens (e.g. Titanium Dioxide, Zinc Oxide) are absorbed through the skin
- Consider these in pregnancy
- Some of the chemical Sunscreens (e.g. Avobenzone, Oxybenzone) may be absorbed through the skin
- No known related safety concerns, but further research is ongoing (see link below)
- Known risk of Sunburn and Skin Cancer outweighs the potential risk of Sunscreen aborption
- Matta (2020) JAMA 323(3):256-67 +PMID: 31961417 [PubMed]
- None of the physical Sunscreens (e.g. Titanium Dioxide, Zinc Oxide) are absorbed through the skin
VIII. Drug Interactions
- Apply Sunscreen at least 15 to 30 minutes after applying Topical Medications
IX. Resources
- FDA Consumer update on Sunscreens and possible absorption
X. References
- (2025) Presc Ins 32(7): 38
- (2020) Presc Lett 27(7): 41
- (2018) Presc Lett 25(7): 39
- (2013) Presc Lett 20(7): 41-2
- Potera (1997) Physician and Sports Med 25(5):117-20
- (1999) Med Lett Drugs Ther, 41(1052): 43-4 [PubMed]
- Wentzell (1996) Am Fam Physician 53(5):1713-19 [PubMed]
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