What is Tanning?
When you’re exposed to the damaging Ultraviolet rays (UVR) from the sun, your body responds by producing more melanin (melanin is a natural skin pigment). This results in skin darkening or skin tanning. Tanning can also be caused by tanning beds.
There are two types of UV radiation in the sun’s rays, UV-A and UV-B. UV-B radiation burns the upper layers of your skin and causes sunburn. UVA radiation is responsible for tanning. The UV-A radiation can travel to the lower layers of the skin, where melanocytes (cells that produce the skin pigment melanin) are present. On exposure to excess UV-A radiation, the melanocytes produce a brown pigment called melanin. Melanin causes darkening of the skin leading to a tan. This protects the skin from burning.
Evolutionary Relevance of Tanning
Tanning is commonly seen in people whose ancestors lived in the mid-latitude regions. The tanning ability evolved in these regions where the sun’s intensity varies with season drastically.
People in this region have moderate levels of melanin pigmentation in their skin to adapt to the varying UV exposure levels.
Research shows that sun-induced folate deficiency is what led to the evolution of dark skin and tanning. Folate is a light-sensitive vitamin needed for cell division and repair. Folate levels are affected by UV rays. In summer, light-skinned people have a higher chance of folate deficiency, whereas, in winter, dark-skinned people will not have sufficient levels of vitamin D. Tanning evolved as an adaptation to these varying levels of sun exposure.
How Genes Influence the Tanning Response?
Genetics is linked to how your skin responds to sunlight exposure. Several genes affect skin color and tanning ability.
A study done at King’s College, London, found 20 genes related to tanning, some of which were previously found to be linked to skin pigmentation. Few of the genes found had no previously documented link to skin pigmentation but had an effect on tanning. This study included a wide range of about 200,000 participants, including people who never tan or burn.
The IRF4 Gene
The IRF4 gene contains instructions for the production of interferon regulatory factor 4. These proteins are mainly involved in the body’s response to infection by viruses.
This gene is also found to be strongly associated with pigmentation, sensitivity to sun exposure, freckles, blue eyes, and brown hair color.
rs12203592
rs12203592 is an SNP found in the IRF4 gene.
The T allele is the risk allele and is associated with a higher sensitivity to sun exposure, freckles, and brown hair.
The T allele is also found to have a significant association with tanning ability.
TYR Gene
The TYR gene contains instructions for the production of an enzyme tyrosinase. This enzyme contains instructions for the production of the skin pigment melanin. Variations in this interfere with melanin production and, as a result, can cause differences in skin pigmentation.
rs1126809
rs1126809 is an SNP found in the TYR gene.
The A allele is associated with a slight increase in skin cancer risk and tanning ability as compared to the G allele.
EXOC2 Gene
The EXOC2 gene contains instructions for the production of Exocyst Complex 2 protein. This protein is part of a multi-protein complex that targets vesicles, which are tiny sacs that transport material in and out of the cells to specific sites on the outer membrane (plasma membrane) of the cell.
Several studies have found a relation between changes in the EXOC2 gene and skin pigmentation.
rs12210050
rs12210050 is an SNP found in the EXOC2 gene.
The T allele [increases the risk of basal cell carcinoma)(https://www.snpedia.com/index.php/Rs12210050) and is found to have a significant association with tanning ability.
Non-genetic Influences on Tanning
Increased exposure to UV light
Exposure to UV light causes the skin cells to produce more melanin, and this leads to tanning.
Indoor tanning
Tanning beds aren’t a safer alternative to sunlight. They use UV radiation to produce a cosmetic tan, which has the same effects as outdoor tanning.
Phototherapy
Phototherapy can cause tanning of the skin as it uses light similar to the sun rays.
Radiation therapy
One of the side effects of radiation therapy is tanning.
Risks of Tanning
- Tanning resulting from exposure to UV rays could indicate cell damage in the outermost layer of the skin.
- Tanning increases your risk for several types of skin cancer, including melanoma, basal cell carcinoma, and squamous cell carcinoma.
- Worldwide, the number of skin cancer cases due to tanning is higher than the number of lung cancer cases due to smoking.
- Premature skin aging is caused by high UV exposure. Visible signs of aging like wrinkles, dark spots, and weathered skin are seen.
- Tanning can increase the risk of eye cataracts in older people.
- Overexposure to UV radiation can suppress the skin’s natural defense and weaken the body’s immune system.
Recommendations to Prevent and Remove a Tan
Avoiding a tan
- The best way to avoid the effects of a tan is to entirely avoid tanning, both indoor and outdoor.
- Protect your skin from sunlight by wearing a hat, sunglasses, and avoiding excess exposure to sunlight.
- Take frequent breaks under the shade to avoid continuous exposure.
- Sunscreen: Use a broad-spectrum sunscreen of SPF30 or greater that blocks both UVA and UVB rays. Make sure to apply enough sunscreen to protect your skin.
Lightening a tan
- Skin-lightening products that contain vitamin C, glycolic acid, retinoids, kojic acid, or azelaic acid can be used. There are various creams available over the counter. Make sure you consult a dermatologist before going ahead with these treatments.
- Exfoliation: Removing the dead skin cells on the surface with a homemade or store-bought scrub can help. Avoid the sun after exfoliation as it makes you more susceptible to tanning and skin damage. You need to give the cells time to heal.
- Home remedies: Aloe is a great anti-inflammatory skin soother that can help remove a tan. Turmeric can help protect against sun damage, but it stains your skin. The stain can be removed immediately with a wash.
- Sunless tanning: Several sunless tanning lotions that contain dihydroxyacetone(DHA) as the active ingredient are available in the market. This temporarily darkens the skin and resembles a tan. The effects last for a few days.
Summary
- Tanning is caused by exposure to UV rays in sunlight. The UV-A component leads to an increase in melanin secretion, which causes darkening of the skin and tanning.
- Tanning is harmful to the cells on the surface of the skin and causes permanent DNA damage. It also increases the risk of skin cancer, eye cataracts, and premature aging.
- Certain genes like IRF4, TYR, and EXOC2 can increase your susceptibility to tanning. All these genes influence pigment regulation and distribution in your body.
- Phototherapy, radiation therapy, increased exposure to UV light, and indoor tanning beds also cause tanning and the harmful effects associated with it.
- The best way to manage a tan is to avoid it by wearing sunscreen and protecting your skin. Several skin-lightening products and home remedies can be used to lighten a tan.
- Sunless tanning products are an alternative to indoor tanning beds and tanning under the sun.
References
https://www.skincancer.org/risk-factors/tanning/#sad
https://www.healthline.com/health/how-to-get-rid-of-a-tan
https://www.fda.gov/radiation-emitting-products/tanning/risks-tanning
https://www.sciencemag.org/news/2010/06/scienceshot-tanning-ability-driven-evolution
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2758927/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3690971/
https://academic.oup.com/endo/article/156/1/39/2800584
https://www.nature.com/articles/s41467-018-04086-y
https://www.sciencemag.org/news/2010/06/scienceshot-tanning-ability-driven-evolution
