Sunscreen

Aka: Sunscreen, Sun Protection Factor

1. See Also
   1. Sun Exposure (lists other preventive measures)
   2. Sun Damaged Skin
   3. Phototoxic Reaction
   4. Sunburn
2. Recommendations
   1. Use Sunscreen with SPF of 15 or higher
   2. Use Sunscreen that blocks UVA and UVB
      1. Most current Sunscreens block UVB
      2. SPF rating does not apply to UVA
      3. Zinc Oxide, Titanium dioxide, Mexoryl block UVA
   3. Shake Sunscreen well before using
   4. 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)
   5. Apply 1 ounce of Sunscreen for whole body
      1. Do not forget around eyes, ears and mouth
      2. Apply to scalp if bald or hair thinning
   6. Reapply Sunscreen hourly when sweaty or wet
   7. Protect babies and children well from Sun Exposure
3. 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. SPF gives no information on Ultraviolet A protection
4. Preparations: 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
5. Preparations: Inorganic opaque compounds (scatter light)
   1. Titanium dioxide
   2. Zinc oxide
6. Efficacy
   1. Reduced with wind, heat, humidity, and altitude
   2. Reduced with poor or inadequate application
      1. Most persons 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
      2. Naylor (1995) Arch Dermatol 131:170
   4. Decreases photoaging
7. Safety
   1. Regular use does not result in Vitamin D Deficiency
8. References
   1. Potera (1997) Physician and Sports Med 25(5):117-20
   2. (1999) Med Lett Drugs Ther, 41(1052): 43-4
   3. Wentzell (1996) Am Fam Physician 53(5):1713-19