What is SPF

SPF stands for Sun Protection Factor.[1] The FDA requires that all sunscreens have and SPF label indicating the level of protection for that sunscreen.[2] The SPF represents a numerical ration between the minimum dose of radiation needed to burn skin protected by the test product and the minimum dose of radiation needed to burn and equivalent area of unprotected skin.[1]

Types of Sunscreen Ingredients

Ingredients in Sunscren

Personal Sun Safety Facts

  • Sunscreen does not completely protect you from the harmful effects of the sun. Even with sunscreen on, one should cover your skin and avoid prolonged periods in direct sunlight, especially if the UV Index is high.[2]
  • Be sure to apply sunscreen 20 minutes before going out into the sun. This allows adequate time for the sunscreen to be absorbed into your skin.[2]
  • If you are planning on swimming or doing a strenuous activity, be sure to apply sunscreen even more frequently. Sweat, water, and actions like towel drying neutralize the effectiveness of sunscreen.
  • Water resistant sunscreens are only required to maintain their SPF for 40 minutes of water exposure and very water resistant need only maintain theirs for 80 minutes. Be sure to re-apply accordingly![2]
  • When applying your sunscreen be sure to cover obscure parts of your body such as lips. Ears, feet, back of the neck, and areas of the body covered by shifting clothing such as hats, jewelry, and straps.[2]
  • Keep babies out of direct sunlight and cover them as completely as possible. The American Academy of Pediatrics recommends applying sunscreen to small areas where clothing does not provide adequate protection (face, back of hands). [2]
  • The idea of a healthy tan is a myth!!!! Any change in you natural skin color is indicative of skin damage![2]
  • A lack of sun exposure will not cause vitamin D deficiency in most people. Vitamin D is generally consumed in adequate amounts in people's diets. If you are concerned about Vitamin D deficiency you should talk to you physician about taking a supplement or other healthier ways of getting the right amount of vitamin D.[2]


  1. Shalka S, Manoel Silva dos Reis V. Sun protection factor: meanings and controversies. Brazilian Association of Dermatology. 2011; 86(3).
  2. The Burning Facts [internet]. Washington D.C: The Environmental Protection Agency; c 2006 [updated 2012 March 06; cited2012 March 18]. Available from: http://www.epa.gov/sunwise/
  3. Sayre M, Dowdy J, Lott D, Marlowe E. Commentary on ‘UVB-SPF’: the SPF labels of sunscreen products convey more than just UVB protection. Photodematology, Photoimmunology, & Photomedicine. 2008; 24: 218-220.
  4. Faurschou A and Wulf H.C. The relationship between sun protection factor and amount of sunscreen applied in vivo. British Journal of Dermatology. 2006; 156: 716-719.

UV4U - Loyola University Maryland