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Science Behind the Sunburn

Contact Author Dakota Blauvelt, PA, reviewed by Mark Trott, M.D., and Antonio Cruz, M.D.
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Many of us are far too familiar with the unsightly consequences of having too much fun in the sun (redness, possibly even swelling, blisters and peeling of the skin), but what isn’t as obvious is the damage being done underneath the skin. 

A sunburn is a preventable risk factor for accelerating aging of the skin and skin cancer. Dermatologists agree that the most effective way to keep skin looking young and healthy is to protect ourselves from the sun. As the season of long sunny days approaches, let’s review why this simple bit of advice is important to adhere to. 

The Time is Right for a Burn

A sunburn is an inflammatory response of the skin caused by excessive ultraviolet radiation (UVR) exposure. Both UVA (320 to 400 nm) and UVB (280 to 320 nm) wavelengths can induce a sunburn; however, UVB are the most successful at provoking erythema (superficial reddening of the skin) and DNA damage.

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No matter how close to the equator your clients may find themselves this summer, remember that UVB intensity is highest everywhere between 10 a.m. and 4 p.m.

The risk of a sunburn is inversely related to latitude, and therefore, the greatest risk is closest to the equator, where UVB intensity is most significant1. No matter how close to the equator your clients may find themselves this summer, remember that UVB intensity is highest everywhere between 10 a.m. and 4 p.m. 

How the Skin Changes

So what exactly is happening to the skin as it’s absorbing all this UVR? UV photons damage the bonds between the four nucleotides that make up cellular DNA (thymine, cytosine, adenine, and guanine). These damaged cells then undergo apoptosis (programmed cell death), which leads to a cascade of unfortunate events.

Within 30 minutes, the superficial blood vessels under the skin begin to vasodilate1. Blood, along with inflammatory mediators, rush to the site of damage to help with the healing process. As a result, we experience redness and painful inflammation of the skin. The acute skin manifestations associated with sunburns typically resolve on their own within three to seven days1

The damage that happens on the cellular level is not always as transient. Sometimes, UVR causes damage to the DNA repair process in a way that allows cells to mutate and acquire the ability to avoid dying, which leads to the disease process known as cancer3.

The Shot Glass Rule to Sunscreen

Skin cancer is the most common form of cancer in the United States4. Susceptibility to a sunburn is a red flag for susceptibility to skin cancer; however, everyone, regardless of skin type, is at risk for the potential adverse effects of UVR. Therefore, the use of sunscreen should be a part of everyone’s daily skin care routine.

Broad-spectrum products with a sun protection factor (SPF) 30 or greater are recommended. Sunscreens should be applied generously, repeatedly and to all parts of the skin that are exposed to the sun.

Studies have shown that the average size adult or child needs about the amount of sunscreen that it takes to fill a shot glass in order to evenly cover the entire body.

Your clients can use the “shot glass rule” when applying sunscreen. Studies have shown that the average size adult or child needs about the amount of sunscreen that it takes to fill a shot glass in order to evenly cover the entire body.

Experts also agree that it is best for sunscreen to be applied 15 to 30 minutes before going out in the sun to allow the formation of a protective barrier and should be re-applied every two hours2. Avoidance of the sun during peak daylight hours and the use of protective sunscreen are vital to keeping your clients’ skin young-looking and cancer-free. 

References:

  1. https://www-uptodate-com.ezproxy.library.tufts.edu/contents/sunburn?source=search_result&search=sunburn&selectedTitle=1~150#H2456151
  2. https://www-uptodate-com.ezproxy.library.tufts.edu/contents/selection-of-sunscreen-and-sun-protective-measures?source=machineLearning&search=how%20to%20use%20sunscreen&selectedTitle=1~150&sectionRank=3&anchor=H11208773#H11208773
  3. http://www.livescience.com/38039-what-causes-sunburns.html
  4. https://www.cdc.gov/cancer/skin/statistics/index.htm  

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