Why Do I Have to Wear Sunscreen? How Does It Protect Our Skin? And What is SPF?

Jul 28 , 2020

Why Do I Have to Wear Sunscreen? How Does It Protect Our Skin? And What is SPF?

by Dr. Suzanne Gokel

Sunscreen helps to protect us from harmful UVA/UVB radiation coming from the sun. Chemical or Organic Sunscreens are the ones most commonly seen. These work by absorbing harmful UV rays to keep them from reaching the skin. Mineral or Inorganic Sunscreens work by creating a physical barrier on the skin to reflect UV rays. Typically this is Titanium dioxide or Zinc Dioxide. These usually last longer on the skin and are better tolerated for those with sensitive skin. Most Sunscreen Formulations are made with a combination of Organic and Inorganic protectants to maximize protection from the sun’s rays.


SPF = Sun Protection Factor. This number has to do with how long an individual can be in the sun before their skin burns or tans. Many people feel that the highest SPF is best. However, the more SPF there is in a product, the amount of protection does not increase linearly. So an SPF 15 gives 93% protection, and SPF of 30 gives 97% and an SPF of 50 or higher only gives small increments of 98% or more. High-number SPFs last the same amount of time as low-number SPFs. Beyond that the higher levels of SPF are more chemicals without much more protection which we try to be mindful of. Dermatologists recommend to use an SPF 15-30 daily and to reapply every 2 hours especially when in prolonged sun exposure, such as a day at the beach.  Most sunscreens are not truly waterproof but water resistant for 40 or 80 minutes. Ideally, apply sunscreen 20-30 min prior to going into water and re-apply when you get out of the water.

Keep in mind for winter and fall, UVA rays penetrate through cloud coverage, windows and glass. Snow, sand, and water increase the need for sunscreen because they reflect the sun’s rays. 

Lastly, don’t skimp when lathering up with your sunscreen. Sunscreens work, but only if you apply it correctly and then reapply as directed! You should use about one ounce when applying it to your body – for  reference that’s about the size of a shot glass. Keep up these simple steps so you can have fun in the sun!


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