Science

Why do we get sunburned?

Nobody likes coming home from a relaxing day at the beach, taking a shower, and lying on the couch to find that most of your body is crimson and painful to touch. We all know that spending time in the sun without protection can lead to the dreaded sunburn, but just exactly how it happens is another matter.

Different types of burns

Up close view of man's bright red shoulder, pointing to sunburn skin damage
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It would stand to reason that the heat of the sun and the burning sensation that follows would have a clear link. However, it is not the heat produced by the sun that causes sunburns. Injuries incurred from external heat sources, such as when touching the stove or stepping on hot asphalt, are classified as thermal burns. These are different from sunburns, which are caused by thermal radiation.

If you remember your high school biology or late night sci-fi, you will recall that one of the major pathways of genetic mutation is through radiation. However, unlike in our favorite sci-fi epics, radiation does not lead to superhuman powers but, rather, to DNA damage.

Ultraviolet radiation

Man floating in pool with bright red sunburn marks across back and shoulders
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Ultraviolet (UV) radiation from the sun damages DNA in skin cells. The primary function of genes is to synthesize, or regulate the synthesis of proteins that serve a plethora of different functions throughout the body. When DNA in our surface skin layer (the epidermis) is damaged, the cells begin to proceed with damage control, releasing prostaglandins and cytokines. These molecular signals trigger dilation of blood vessels and inflammation at the site of damage.

However, this process takes time, and it’s for this reason that the effects of sunburn don’t settle in until four to six hours after prolonged exposure to UV radiation.

Melanoma

Woman standing on beach with deep sunburn and tan lines covering back
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As you likely already know, repeated sunburns pose a risk of developing cancer through mechanisms that are relatively self-evident. Your body has safeguards against errors in DNA replication that protect you from cancer every time something goes wrong with a cell. However, repeated DNA damage increases the chance of developing a mutation that the body cannot detect or fight, and cancer develops therein.

While there are a variety of different types of skin cancer, one of the most well-known and prevalent is melanoma. Melanoma derives its name from the site of its origin: melanocytes. These skin cells are responsible for producing melanin, which gives our skin its color. When stimulated by sunlight, melanocytes produce more melanin, resulting in that ever-coveted golden tan. However, when melanocytes are mutated from repeated DNA damage, they grow uncontrollably and present as skin tags, moles, and various other blemishes that are actually the early signs of a tumor.

Identifying melanoma

Man visits doctor, using magnifying glass to assess moles and possible melanoma on patient's back
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With early detection, the survival rate for melanoma is 98 percent. It’s vital to recognize early signs in the event that you are experiencing an abnormal skin growth. It’s also worth keeping a vigilant eye if you spend a lot of time in the sun. The “ABCDEs” of melanoma are a pneumonic to help identify symptoms of malignant skin growths:

  • Asymmetry: Whereas normal moles are round or ovular, melanoma is often asymmetrical.
  • Border: Melanoma tends to present with uneven borders.
  • Color: Whenever a skin growth aside from a zit or a cyst has multiple colors (such as blue, red, and white), it is a dangerous sign.
  • Diameter: Whenever a novel skin growth is larger than the size of a pencil eraser, you should see a doctor
  • Evolving: Skin growths that change over time in size, color, or shape should be evaluated by a physician.

Stay safe

Parent and child at beach, with parent applying sunscreen to child's back before swimming
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It should go without saying that you should wear sunscreen with appropriate SPF and broad-spectrum coverage whenever you anticipate spending a significant amount of time in the sun. In the event that you haven’t, keep an eye out for the aforementioned warning signs.