A visible tan line on a woman whose skin has been darkened by ultraviolet exposure, except where covered

Sun tanning or tanning is the process whereby skin color is darkened or tanned. It is most often a result of exposure to ultraviolet (UV) radiation from sunlight or from artificial sources, such as a tanning lamp found in indoor tanning beds. People who deliberately tan their skin by exposure to the sun engage in a passive recreational activity of sun bathing. Some people use chemical products which can produce a tanning effect without exposure to ultraviolet radiation, known as sunless tanning.

Impact on skin health

Moderate exposure

A sun tanned arm showing browner skin where it has been exposed

Moderate exposure to direct sunlight contributes to the production of melanin and vitamin D by the body.

Excessive exposure

Excessive exposure to ultraviolet rays has negative health effects, including sunburn. Some people tan or sunburn more easily than others. This may be the result of different skin types and natural skin color, and these may be a result of genetics.[1][2] The term "tanning" has a cultural origin, arising from the color tan. Its origin lies in the Western culture of Europe when it became fashionable for young women to seek a less pale complexion (see Cultural history below).

Long-term

Photoaging of a woman

Excessive exposure may in the long-term increase the risk of skin cancer,[3] as well as depressed immune system function and accelerated aging of the skin.[4]

Tanning process

Melanin is a natural pigment produced by cells called melanocytes in a process called melanogenesis. Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Melanin protects the body by absorbing ultraviolet radiation. Excessive UV radiation causes sunburn along with other direct and indirect DNA damage to the skin, and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens. The tanning process can be triggered by natural sunlight or by artificial UV radiation, which can be delivered in frequencies of UVA, UVB, or a combination of both.[5] The intensity is commonly measured by the UV Index.[6]

Cross-sectional view showing skin tone becoming darker due to the production of more melanin to overcome DNA damage caused by UV radiation

There are two different mechanisms involved in the production of a tan by UV exposure: Firstly, UVA radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin. UVA may also cause melanin to be redistributed (released from melanocytes where it is already stored), but its total quantity is unchanged. Skin darkening from UVA exposure does not lead to significantly increased production of melanin or protection against sunburn.[7] In the second process, triggered primarily by UVB, there is an increase in production of melanin (melanogenesis),[8] which is the body's reaction to direct DNA photodamage (formation of pyrimidine dimers) from UV radiation.[9] Melanogenesis leads to delayed tanning, and typically becomes visible two or three days after exposure.[8] The tan that is created by increased melanogenesis typically lasts for a few weeks or months, much longer than the tan that is caused by oxidation of existing melanin, and is also actually protective against UV skin damage and sunburn, rather than simply cosmetic. Typically, it can provide a modest Sun Protection Factor (SPF) of 3, meaning that tanned skin would tolerate up to 3 times the UV exposure as pale skin.[10] However, in order to cause true melanogenesis-tanning by means of UV exposure, some direct DNA photodamage must first be produced, and this requires UVB exposure (as present in natural sunlight, or sunlamps that produce UVB). The ultraviolet frequencies responsible for tanning are often divided into the UVA and UVB ranges.

UVA

Ultraviolet A (UVA) radiation is in the wavelength range 320 to 400 nm.[11] It is present more uniformly throughout the day, and throughout the year, than UVB. Most UVA is not blocked by the atmosphere's ozone layer. UVA causes the release of existing melanin from the melanocytes to combine with oxygen (oxidize) to create the actual tan color in the skin. UVA is blocked less than UVB by many sunscreens, but is blocked to some degree by clothing. UVA is known both to cause DNA damage and to be carcinogenic. However, it operates not by inducing direct DNA damage, but by producing reactive oxygen species which damage DNA indirectly. UVA (see above) induces a cosmetic tan but little extra melanin protection against sun damage, sun burn, or cancer.

UVB

Ultraviolet B (UVB) radiation is in the wavelength range 280 to 320 nm. Much of this band is blocked by the Earth's ozone layer, but some penetrates. UVB:

  • triggers the formation of CPD-DNA damage (direct DNA damage), which in turn induces an increased melanin production.[9]
  • is more likely to cause a sunburn than UVA as a result of overexposure. The mechanism for sunburn and increased melanogenesis is identical.[12] Both are caused by the direct DNA damage (formation of CPDs).
  • produces Vitamin D in human skin.
  • is reduced by virtually all sunscreens in accordance with their SPF.
  • is thought, but not proven, to cause the formation of moles and some types of skin cancer.
  • causes skin aging (but at a slower rate than UVA).
  • stimulates the production of new melanin, which leads to an increase in the dark-colored pigment within a few days.[13]

Tanning behavior of different skin colors

A person's natural skin color affects their reaction to exposure to sunlight. An individual's natural skin color can vary from a dark brown to a nearly colorless pigmentation, which may appear white. In 1975, Harvard dermatologist Thomas B. Fitzpatrick devised the Fitzpatrick scale which described the common tanning behavior of various skin types, as follows:[14][15]

TypeAlso calledSunburningTanning behaviorvon Luschan scale
IVery light or paleOftenOccasionally1–5
IILight or light-skinnedUsuallySometimes6–10
IIILight intermediateRarelyUsually11–15
IVDark intermediateRarelyOften16–21
VDark or "brown" typeNoSometimes darkens22–28
VIVery dark or "black" typeNoNaturally black-brown skin29–36

Health aspects

Sunburn peeling
Disappearing sun tan, revealing the individual's naturally light-colored skin

The most common risk of exposure to ultraviolet radiation is sunburn, the speed and severity of which vary among individuals. This can be alleviated at least to some extent by the prior application of a suitable-strength sunscreen, which will also hinder the tanning process due to the blocking of UV light. Overexposure to ultraviolet radiation is known to cause skin cancer,[16] make skin age and wrinkle faster,[17] mutate DNA,[18] and impair the immune system.[19] Frequent tanning bed use triples the risk of developing melanoma, the deadliest form of skin cancer, according to a 2010 study. The study suggests that the melanoma risk is linked more closely to total exposure than it is to the age at which an individual first uses a tanning bed.[20] The International Agency for Research on Cancer places the use of tanning beds in the highest cancer risk category, describing them as carcinogenic to humans even if used as recommended. Frequent tanning also has behavioural reinforcing effects,[21] following UVA radiation epidermal keratinocytes synthesize POMC inducing the production of β-Endorphins which are opioid agonists. An opioid blockade will also then cause withdrawal signs after habitual UV exposure leading to many tanners meeting the DSM-IV criteria for addiction.[22] Several organizations, such as the World Health Organization (WHO), the American Cancer Society and the US Surgeon General have issued guidelines warning about sun tanning and UV radiation exposure, either from the sun or from indoor tanning.[23][24][25] Production of vitamin D is essential for human health. Moderate exposure (avoiding sunburn) to UV radiation provides benefits such as increased vitamin D, as well as other possible benefits that are still being studied.[26] Several tanning activators have used different forms of psoralen, which are known to be photocarcinogenic.[27][28][29] Health authorities have banned psoralen since July 1996.[30]

Cultural history

La promenade (1875) by Claude Monet. At that time in the West, the upper social class used parasols, long sleeves and hats to avoid sunlight's tanning effects.

In the United States and Western Europe before the 1920s, tanned skin was associated with the lower classes because they worked outdoors and were exposed to the sunlight. Parasols and long sleeves were typically worn, even at beaches.[31] By the 1920s, however, a cultural transformation took place, and tan skin became the ideal.[31]

By the early 20th century, therapeutic benefits of sunlight were advertised to the public.[32] In 1903, Niels Finsen was awarded the Nobel Prize in Medicine for his “Finsen Light Therapy”.[33] The therapy was a cure for diseases such as lupus vulgaris and rickets. Vitamin D deficiency was found to be a cause of rickets, and exposure to sunlight would allow vitamin D to be produced in a person. Therefore, sunlight exposure was a remedy to curing several diseases, especially rickets.

In 1910 a scientific expedition went to the island of Tenerife to test the wider health benefits of "heliotherapy",[34] and by 1913 "sunbathing" was referred to as a desirable activity for the leisured class.[35] Shortly thereafter, in the 1920s, fashion-designer Coco Chanel accidentally got sunburnt while visiting the French Riviera. When she arrived home, she arrived with a sun tan and her fans apparently liked the look and started to adopt darker skin tones themselves. Tanned skin became a trend partly because of Coco's status and the longing for her lifestyle by other members of society. In addition, Parisians fell in love with Josephine Baker, a "caramel-skinned" singer in Paris, and idolized her darker skin. These two women were leading figures of the transformation that tan skin underwent, in which it became perceived as fashionable, healthy, and luxurious.[36][37][38] Jean Patou capitalized on the new tanning fad, launching the first sun tan oil "Huile de Chaldee" in 1927.[39] Just before the 1930s, sunlight therapy became a popularly subscribed cure for almost every ailment from simple fatigue to tuberculosis. In the 1940s, advertisements started appearing in women's magazines which encouraged sunbathing. At the same time, swimsuits' skin coverage began decreasing, with the bikini radically changing swimsuit style after it made its appearance in 1946. In the 1950s, many people used baby oil as a method to increase tanning.

Coppertone, in 1953, marketed its sunscreen with a drawing of a young girl and her cocker spaniel tugging on her bathing suit bottom, revealing her bare bottom and tan line; this advertisement was modified around the turn of the 21st century and now shows a little girl wearing a one-piece bathing suit or shorts.[40] In the latter part of the 1950s, silver metallic reflectors were common to enhance one's tan.[41] In 1962, sunscreen commenced to be SPF rated, although SPF labeling in the US was not standardized by the FDA until 1978. In the 1970s, Mattel introduced Malibu Barbie, which had tanned skin and further popularized sun tanning among women.[42][43]

In 1978, both sunscreen with an SPF 15 rating as well as tanning beds first appeared. In 2007, there were an estimated 50,000 outlets for indoor tanning; it was a five-billion-dollar industry in the United States,[44] and had spawned an auxiliary industry for indoor tanning lotions including bronzers, intensifiers, and accelerators. Since then, the indoor tanning industry has become more constrained by health regulations.[45] In China, darker skin is still considered by many to be the mark of the lower classes. As recently as 2012, in some parts of China, ski masks were becoming popular items to wear at the beach in order to protect the wearer's face from the effects of sunlight.[46] A 1969 innovation is tan-through swimwear, which uses fabric perforated with thousands of micro holes that are nearly invisible to the naked eye, but which transmit enough sunlight to approach an all-over tan, especially if the fabric is stretched taut. Tan-through swimwear typically allows more than one-third of UV rays to pass through (equivalent to SPF 3 or less), and an application of sunscreen even to the covered area is recommended.[47][48][49]

Sunless tanning

A tanning bed emits UV radiation.

To avoid exposure to UVB and UVA rays, or in seasons without strong sunshine, some people take alternative steps to appear with darkened skin. They may use sunless tanning (also known as self-tanners); stainers which are based on dihydroxyacetone (DHA);[50] or cosmetics such as bronzers. Many sunless tanning products are available in the form of darkening creams, gels, lotions, and sprays that are self-applied on the skin. There is also a professional spray-on tanning option or “tanning booth” that is offered by spas, salons, and tanning businesses.[51] Spray tanning does not involve a color being sprayed on the body, instead it uses a colorless chemical which reacts with proteins in the top layer of the skin, resulting in a brown color.

See also

References

  1. ↑ Marshall, Jessica. "Gene behind tanning comes out of hiding". New Scientist. Archived from the original on 25 November 2020. Retrieved 28 October 2020.
  2. ↑ "Scientists find why some people tan and some people burn". The Independent. 8 May 2018. Archived from the original on 25 May 2022.
  3. ↑ "Ultraviolet (UV) Radiation". Archived from the original on 6 September 2015. Retrieved 27 August 2015.
  4. ↑ Amaro-Ortiz, Alexandra; Yan, Betty; D’Orazio, John A. (15 May 2014). "Ultraviolet Radiation, Aging and the Skin: Prevention of Damage by Topical cAMP Manipulation". Molecules. 19 (5): 6202–6219. doi:10.3390/molecules19056202. ISSN 1420-3049. PMC 4344124. PMID 24838074.
  5. ↑ Garone, Michael; Howard, John; Fabrikant, Jordan (February 2015). "A Review of Common Tanning Methods". The Journal of Clinical and Aesthetic Dermatology. 8 (2): 43–47. ISSN 1941-2789. PMC 4345932. PMID 25741402.
  6. ↑ Encyclopædia Britannica almanac 2010. Chicago: Encyclopædia Britannica. 2009. ISBN 978-1615353293.
  7. ↑ Miyamura Y; Coelho SG; Schlenz K; et al. (February 2011). "The deceptive nature of UVA tanning versus the modest protective effects of UVB tanning on human skin". Pigment Cell & Melanoma Research. 24 (1): 136–147. doi:10.1111/j.1755-148X.2010.00764.x. PMC 3021652. PMID 20979596.
  8. 1 2 Amy Thorlin (5 February 2006). "The Tanning Process". Lookingfit.com. Archived from the original on 22 July 2009. Retrieved 15 April 2015.
  9. 1 2 Nita Agar; Antony R. Young (2005). "Review: Melanogenesis: a photoprotective response to DNA damage?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis. 571 (1–2): 121–132. doi:10.1016/j.mrfmmm.2004.11.016. PMID 15748643.
  10. ↑ "The Surgeon General's Call to Action to Prevent Skin Cancer" (PDF). U.S. Department of Health and Human Services. 2014. p. 20. Archived (PDF) from the original on 26 November 2014. A UVB-induced tan provides minimal sun protection, equivalent to an SPF of about 3.
  11. ↑ "ISO 21348 Definitions of Solar Irradiance Spectral Categories" (PDF). Archived (PDF) from the original on 29 October 2013.
  12. ↑ John A. Parrish; Kurt F. Jaenicke; R. Rox Anderson (1982). "Erythema And Melanogenesis Action Spectra Of Normal Human Skin". Photochemistry and Photobiology. 36 (2): 187–191. doi:10.1111/j.1751-1097.1982.tb04362.x. PMID 7122713. S2CID 38940583.
  13. ↑ "The known health effects of UV". WHO. 1 December 2010. Archived from the original on 4 August 2012. Retrieved 1 August 2012.
  14. ↑ Fitzpatrick TB: Soleil et peau [Sun and skin]. Journal de Médecine Esthétique 1975; 2:33-34
  15. ↑ Weller, R; J Hunter; J Savin; M Dahl (2008). Clinical Dermatology (4th ed.). Malden, Massachusetts, USA: Blackwell Publishing. p. 268. ISBN 978-1-4051-4663-0.
  16. ↑ "Reviewed Substances". ntp.niehs.nih.gov. Archived from the original on 16 December 2016. Retrieved 13 December 2016.
  17. ↑ Fisher GJ, Wang ZQ, Datta SC, Varani J, Kang S, Voorhees JJ (November 1997). "Pathophysiology of premature skin aging induced by ultraviolet light". N. Engl. J. Med. 337 (20): 1419–28. doi:10.1056/NEJM199711133372003. PMID 9358139.
  18. ↑ Sinha RP, Häder DP (April 2002). "UV-induced DNA damage and repair: a review". Photochem. Photobiol. Sci. 1 (4): 225–36. doi:10.1039/B201230H. PMID 12661961.
  19. ↑ Baadsgaard O (January 1991). "In vivo ultraviolet irradiation of human skin results in profound perturbation of the immune system. Relevance to ultraviolet-induced skin cancer". Arch Dermatol. 127 (1): 99–109. doi:10.1001/archderm.1991.01680010109019. PMID 1824747.
  20. ↑ Peeples, Lynne. Study: Frequent tanning-bed use triples melanoma risk. Archived 30 May 2010 at the Wayback Machine CNN, 27 May 2010.
  21. ↑ Kaur, Mandeep; Liguori, Anthony; Lang, Wei; Rapp, Stephen R.; Fleischer, Alan B.; Feldman, Steven R. (1 April 2006). "Induction of withdrawal-like symptoms in a small randomized, controlled trial of opioid blockade in frequent tanners". Journal of the American Academy of Dermatology. 54 (4): 709–711. doi:10.1016/j.jaad.2005.11.1059. ISSN 0190-9622. PMID 16546596.
  22. ↑ "Side effects of naltrexone observed in frequent tanners: Could frequent tanners have ultraviolet-induced high opioid levels?". pdfslide.us. Archived from the original on 7 March 2022. Retrieved 7 March 2022.
  23. ↑ Sunscreens - IARC Handbook of Cancer Prevention Volume 5. ISBN 9789283230052. Archived from the original on 11 February 2017. Retrieved 9 February 2017. {{cite book}}: |website= ignored (help)
  24. ↑ "Skin Cancer". www.cancer.org. Archived from the original on 17 January 2017. Retrieved 9 February 2017.
  25. ↑ General, Office of the Surgeon. "The Surgeon General's Call to Action to Prevent Skin Cancer". www.surgeongeneral.gov. Archived from the original on 9 February 2017. Retrieved 9 February 2017.
  26. ↑ Baggerly, Carole A.; Cuomo, Raphael E.; French, Christine B.; Garland, Cedric F.; Gorham, Edward D.; Grant, William B.; Heaney, Robert P.; Holick, Michael F.; Hollis, Bruce W.; McDonnell, Sharon L.; Pittaway, Mary; Seaton, Paul; Wagner, Carol L.; Wunsch, Alexander (22 June 2015). "Sunlight and Vitamin D: Necessary for Public Health". Journal of the American College of Nutrition. 34 (4): 359–365. doi:10.1080/07315724.2015.1039866. PMC 4536937. PMID 26098394.
  27. ↑ Ashwood-Smith MJ. (1979). "Possible cancer hazard associated with 5-methoxypsoralen in sun tan preparations". BMJ. 2 (6198): 1144. doi:10.1136/bmj.2.6198.1144-b. PMC 1596980. PMID 519338.
  28. ↑ M. J. Ashwood-Smith; G. A. Poulton; M. Barker; M. Mildenberger E. (1980). "5-Methoxypsoralen, an ingredient in several sun tan preparations, has lethal, mutagenic and clastogenic properties". Nature. 285 (5): 407–409. Bibcode:1980Natur.285..407A. doi:10.1038/285407a0. PMID 6991953. S2CID 4345680.
  29. ↑ Zajdela F, Bisagni E (1981). "5-Methoxypsoralen, the melanogenic additive in sun-tan preparations, is tumorigenic in mice exposed to 365 nm UV radiation". Carcinogenesis. 2 (2): 121–7. doi:10.1093/carcin/2.2.121. PMID 7273295.
  30. ↑ Autier P.; Dore J.-F.; Cesarini J.-P. (1997). "Should subjects who used psoralen sun tan activators be screened for melanoma?". Annals of Oncology. 8 (5): 435–437. doi:10.1023/A:1008205513771. PMID 9233521.
  31. 1 2 Singer, Merrill; Hans Baer (28 July 2008). Killer Commodities: Public Health and the Corporate Production of Harm. AltaMira Press. p. 151. ISBN 978-0-7591-0979-7. Retrieved 11 September 2009. Harris investigated the history of the parasol... everywhere ordinary people were forbidden to protect themselves with such devices "pallid skin became a marker of upper-class status". At the beginning of the 20th Century, in the United States, lighter-skinned people avoided the sun. ... Tanned skin was considered lower class...But by the 1920s, a cultural transformation in favor of sun tanning took place.
  32. ↑ "The Times". 25 August 1900: 1: An advertisement for a 'German Bath In Scotland' offers 'For Health and Pleasure...Pure Air and Sun Baths...'. {{cite journal}}: Cite journal requires |journal= (help)
  33. ↑ "All Nobel Laureates in Physiology or Medicine". Nobel Media. Archived from the original on 12 May 2015. Retrieved 29 April 2015.
  34. ↑ "The Times". 12 March 1910: 12. {{cite journal}}: Cite journal requires |journal= (help)
  35. ↑ "The Times". 4 September 1913: 6. {{cite journal}}: Cite journal requires |journal= (help):Describing a visit by the Prince of Wales to the pretty town of Sigmaringen the reporter says: ‘The Castle possesses many delightful terraces which could be adapted for sunbathing.’
  36. ↑ Hanson, Peter G. (22 June 2009). "About Face". The Effects of Aging, Health and Stress on Your Face. FaceMaster. Archived from the original on 23 April 2012.{{cite web}}: CS1 maint: unfit URL (link)
  37. ↑ "Sun and Clouds: The Sun in History". Magic Bullets - Chemistry vs. Cancer. The Chemical Heritage Foundation. 2001. Archived from the original on 20 June 2010. By the 1920s, the therapeutic effect of the sun was widely promoted, and two well-publicized French personalities gave "tanning" a fashion boost. Coco Chanel, of designer fame, returned to Paris after a cruise on the Duke of Westminster's yacht with a tan that became all the rage. And the natural caramel skin color of singer Josephine Baker made women all over the world try to emulate her skin tone.{{cite web}}: CS1 maint: unfit URL (link)
  38. ↑ Koskoff, Sharon (28 May 2007). Art Deco of the Palm Beaches. Arcadia Publishing. p. 2. ISBN 978-0-7385-4415-1. Retrieved 11 September 2009. In 1920s France, the caramel-skinned entertainer Josephine Baker became a Parisian idol. Concurrently, fashion designer Coco Chanel was "bronzed" while cruising on a yacht. A winter tan became a symbol of the leisure class and showed you could afford to travel to exotic climates.
  39. ↑ Steele, Valerie, ed. (2010). The Berg Companion to Fashion. Berg. p. 554. ISBN 978-1847885630.
  40. ↑ "Sunscreen Lotion, Spray & Sun Care Products - Coppertone® - Coppertone®". www.coppertone.com. Archived from the original on 26 October 2016. Retrieved 1 May 2018.
  41. ↑ Campo, Riku (31 August 2010). Best in Beauty: An Ultimate Guide to Makeup and Skincare Techniques, Tools, and Products. Simon and Schuster. p. 185. ISBN 978-1-4391-5585-1.
  42. ↑ Heckman, Carolyn J.; Manne, Sharon L. (15 September 2011). Shedding Light on Indoor Tanning. Springer Science & Business Media. p. 20. ISBN 978-94-007-2048-0.
  43. ↑ Jablonski, Nina G. (27 September 2012). Living Color: The Biological and Social Meaning of Skin Color. University of California Press. p. 185. ISBN 978-0-520-25153-3.
  44. ↑ Wright, Dan (16 August 2007). "Working The Tan". The Daily News-Record. Harrisonburg, Virginia. Archived from the original on 20 April 2010. Retrieved 11 September 2009. The tanning industry has grown about 25 percent over the past six years, according to the Indoor Tanning Association. In the United States, about 25,000 free-standing tanning salons employ 160,000 people and generate more than $5 billion in annual revenue, the association said.
  45. ↑ Clark, Patrick (5 October 2016). "Twilight of the Tanning Salons". Bloomberg News. Archived from the original on 10 October 2016. Retrieved 9 October 2016.
  46. ↑ Levin, Dan (3 August 2012). "Beach Essentials in China: Flip-Flops, a Towel and a Ski Mask". The New York Times. Archived from the original on 5 August 2012. Retrieved 5 August 2012.
  47. ↑ Taylor, Angela (17 October 1969). "Tan-Through Fabric Lets Sun Shine In". The New York Times. p. 55. Archived from the original on 12 October 2013. Retrieved 30 November 2014.
  48. ↑ "Scorecard: No nudes is good news". Sports Illustrated. 1 September 1969. Archived from the original on 12 October 2013. permits 40% of the sun's ultraviolet rays{{cite news}}: CS1 maint: unfit URL (link)
  49. ↑ "Tan-tastic bikini that lets rays shine through". Daily Express. 30 May 2009. Archived from the original on 17 October 2014. Retrieved 17 September 2014. 80 per cent of UV rays... a stretchy yarn described as 'a chicken wire mesh material'
  50. ↑ "Dihydroxyacetone". Archived from the original on 28 July 2010. Retrieved 6 July 2010.
  51. ↑ "Sunless tanning: A safe alternative to sunbathing". Archived from the original on 16 February 2010. Retrieved 6 July 2010.
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