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What Exactly Happens When We Tan or Sunburn?

Updated: Mar 5

Author: Silvia DiPaola

Editor: Laine Xu

Artist: Daisy Zheng

Many people like to take advantage of the sun during the summer months and receive a golden tan, but what physically occurs in the body to cause the skin to darken? The answer can be found in the two types of rays that the sun emits: UVA and UVB rays!

95% percent of the sun’s rays that reach the earth are UVA, while the other 5% consists of UVBs. UVA rays usually cause one to tan, while UVB rays typically cause sunburns. UVA rays penetrate the skin down to the lower layers of the epidermis; this triggers cells called melanocytes (pigment cells) to produce a brown pigment called melanin. Melanin substance is produced to prevent UV radiation from damaging cells closer to the surface of the skin. It also serves to prevent the skin from burning. The melanin then begins to pile up on the cells; the higher the piles are, the darker the skin becomes. Thus, the longer one stays out in the sun, the more melanin is produced, and the more tan the skin becomes. However, tanning is considered to be skin damage. This is because it occurs as a response to mutations that occur in the DNA when cells are struck by UV rays.

UVB rays specifically penetrate only the upper layers of the skin (the epidermis). Overexposure to them causes sunburns to appear on the skin. They directly damage DNA and thus are a major cause of skin cancer development. Although UVA rays usually do not cause sunburn, they penetrate the skin deeper than UVB rays do. Since they penetrate the dermis layer, where the blood vessels and nerves are housed, these rays may damage one’s immune system. However, they cause indirect damage to DNA, as opposed to UVB rays that inflict direct damage. UVA rays in particular lead to premature skin aging manifested in the form of wrinkles.

As we can see, tanning can have serious health consequences due to the sheer penetrating power of the sun’s powerful rays. Exposing oneself to UVA and UVB rays can cause premature skin aging, sunburn, DNA damage, and increased risk of developing skin cancers such as melanoma. It is imperative that one wears sunscreen (SPF 30+) when outside for prolonged periods. Although it may look nice to have bronze skin during the summertime, it is crucial to understand the potentially serious damage that is occurring to the skin in the process!



“Tanning (for Teens) - Nemours KidsHealth.” Edited by Patrice M Hyde, KidsHealth, The

Nemours Foundation, Aug. 2016,

Vandergriendt, Carly. “UVA vs. UVB Rays: What's the Difference?” Healthline, Healthline

Media, 12 Sept. 2019,

Winderl, Amy Marturana. “This Is What Actually Happens to Your Skin When You Get a

Tan.” SELF, Condé Nast, 8 June 2016,

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