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Sunscreen

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Sunscreen, Sun Protection Factor, SPF, Titanium Dioxide, Topical Zinc Oxide, Oxybenzone, Octinoxate, Menthyl Anthranilate, Avobenzone, Drometrizole

  • See Also
  1. Sun Exposure (lists other preventive measures)
  2. Sun Damaged Skin
  3. Phototoxic Reaction
  4. Sunburn
  • Technique
  1. Use Sunscreen with SPF of 15 or higher
    1. SPF 15-30 is typically sufficient protection for most patients
      1. SPF 15 blocks 93% of UVB
      2. SPF 30 blocks 97% of UVB
    2. SPF 50 may be considered for patients at high risk of Skin Cancer
      1. SPF 50 blocks 98% of UVB
    3. SPF above 50 is unlikely to provide additional benefit
      1. No added protection or prolonged duration of activity
  2. Use Sunscreen that blocks UVA and UVB
    1. Most current Sunscreens block UVB
    2. SPF rating does not apply to UVA
    3. "Broad spectrum" denotes protection for both UVA and UVB
      1. Zinc Oxide
      2. Titanium Dioxide
      3. Drometrizole trisiloxane (Mexoryl)
  3. Shake Sunscreen well before using
  4. Darker skinned patients should use Sunscreen
    1. Although high Melanin concentrations reduce UV penetration, it does not eliminate UV-induced Skin Cancer
    2. Sheer Sunscreens and dark-tint Sunscreens are available which may be more cosmetically acceptable for patients
  5. Avoid spraying Sunscreen on face
    1. Risk of inhalation
    2. Spray Sunscreen onto hands and then apply to face
  6. Wear Sunscreen on all outdoor daylight exposures
    1. Cloudy days: 80% UV radiation penetrates clouds
    2. Swimming: 50% UV radiation penetrates water
    3. High altitude (UVB increases 8-10% per 1000 feet)
    4. Exposure to snow or water (reflective surface)
  7. Apply 2-3 tablespoons (1 ounce or shot glass size) of Sunscreen for whole body
    1. Do not forget around eyes, ears and mouth
    2. Apply to scalp if bald or hair thinning
  8. Apply Sunscreen 15 minutes before exposure and then every 2 hours (regardless of SPF)
    1. Reapply Sunscreen every 1 hour when sweaty or wet
    2. Water resistant (or water proof) sun screens require the same frequent replacement when wet
  9. Protect babies and children well from Sun Exposure
    1. Keep infants under 6 months in shade or covered
    2. If unable to keep out of sunlight, use a physical Sunscreen
      1. Apply zinc oxide or Titanium Dioxide containing Sunscreen for maximal protection
  10. Replace old Sunscreens
    1. Changed colors
    2. Significantly past their expiration dates (esp. if exposed to Temperature extremes)
  11. Protective Clothing
    1. Covering skin with Ultraviolet Protection Factor (UPF) Clothing also offers sun protection
  • Physiology
  1. Sun Protection Factor (SPF) ratio
    1. Time to produce slight erythema on suncreened skin to
    2. Time to produce same erythema without Sunscreen
  2. SPF Interpretation
    1. "Broad spectrum" denotes protection for both UVA and UVB
    2. SPF gives no information on Ultraviolet A protection
    3. SPF reflects protection from UVB Light
      1. SPF 15 blocks 93% of UVB
      2. SPF 30 blocks 97% of UVB
      3. SPF 50 blocks 98% of UVB
  • Preparations
  • Chemical or Organic Sunscreens
  1. Avobenzone (Parsol 1789)
    1. Absorbs both short and long wavelength Ultraviolet A
    2. Does not absorb Ultraviolet B (UVB)
    3. May be degraded by sunlight exposure
  2. Menthyl Anthranilate
    1. Absorbs shorter wave length Ultraviolet A
  3. Oxybenzone
    1. Absorbs shorter wave length Ultraviolet A
    2. Banned in Hawaii as of 2021 due to adverse effects to ocean wildlife (coral bleaching, reproduction)
  4. Octinoxate
    1. Absorbs UVB
    2. Banned in Hawaii as of 2021 due to adverse effects to ocean wildlife (coral bleaching, reproduction)
  • Preparations
  • Physical, Mineral or Inorganic opaque compounds (scatter light)
  1. Types
    1. Titanium Dioxide
    2. Zinc oxide
  2. Nanoparticles
    1. All physical Sunscreens are classified as nanoparticle, even if they are advertised as "non-nano"
    2. None of the physical Sunscreens are absorbed through the skin regardless of size (nano or "non-nano")
    3. Nanoparticle Sunscreens are typically easier to apply
    4. Nanoparticle size may have environmental impact, but the effects are not currently known
  • Efficacy
  1. Reduced with wind, heat, humidity, and altitude
  2. Reduced with poor or inadequate application
    1. Most people do not apply enough Sunscreen
    2. Multiple layers required to reach listed SPF
  3. Reduces Incidence of Actinic Keratoses
    1. Thompson (1993) N Engl J Med 329:1147 [PubMed]
    2. Naylor (1995) Arch Dermatol 131:170 [PubMed]
  4. Decreases photoaging
  • Safety
  1. Regular Sunscreen use does NOT result in Vitamin D Deficiency in most patients
    1. However, Vitamin D may be reduced 30% in those who regularly use Sunscreen and protective clothing
    2. Passeron (2019) Br J Dermatol 181(5):916-31 +PMID: 31069788 [PubMed]
  2. Oxybenzone, zinc oxide and Titanium Dioxide are safe on skin
  3. Reef safe labeling
    1. Some products, such as Oxybenzone, have been associated with coral reaf bleaching
    2. Some regions (e.g. Hawaii) have banned Oxybenzone, Octinoxate, Avobenzone, Octocrylene
    3. Physical Sunscreens (zinc oxide, Titanium Dioxide) are very effective and are considered "reef safe"
      1. However "reef safe" has no standard definition
      2. Use of effective Sunscreen is paramount in the prevention of Skin Cancer (esp. in reef regions)
  4. Absorption
    1. None of the physical Sunscreens (e.g. Titanium Dioxide, Zinc oxide) are absorbed through the skin
      1. Consider these in pregnancy
    2. Some of the chemical Sunscreens (e.g. Avobenzone, Oxybenzone) may be absorbed through the skin
      1. No known related safety concerns, but further research is ongoing (see link below)
      2. Known risk of Sunburn and Skin Cancer outweighs the potential risk of Sunscreen aborption
      3. Matta (2020) JAMA 323(3):256-67 +PMID: 31961417 [PubMed]
  • Drug Interactions
  1. Apply Sunscreen at least 15 to 30 minutes after applying Topical Medications
  • Resources
  1. FDA Consumer update on Sunscreens and possible absorption
    1. https://www.fda.gov/news-events/fda-voices/shedding-more-light-sunscreen-absorption
  • References
  1. (2025) Presc Ins 32(7): 38
  2. (2020) Presc Lett 27(7): 41
  3. (2018) Presc Lett 25(7): 39
  4. (2013) Presc Lett 20(7): 41-2
  5. Potera (1997) Physician and Sports Med 25(5):117-20
  6. (1999) Med Lett Drugs Ther, 41(1052): 43-4 [PubMed]
  7. Wentzell (1996) Am Fam Physician 53(5):1713-19 [PubMed]