Skin tanning (sun bathing)

Skin obtained from animal after slaughtering is brought in tannery for making a useful product this is carried out through tanning by mean of chemical and then dyeing and finishing. Animal skin tanning during live is not in practice.
But some humans are very fond of their skin tanning especially who has white skin and this skin tanning of human is carried out in sitting directing in sun light artificial tanning baths. Sun tanning is the act of exposing the skin to ultraviolet (UV) radiation, for the purpose of darkening skin color, either during sun bathing or using artificial sources, such as tanning beds.
Tanning is a natural process, whereby the skin creates the brown-colored pigment called melanin, to protect it against the harmful UV rays in sunlight, but operates equally with artificial UV radiation. There are two different mechanisms involved.
Firstly, the UVA-radiation generates oxidative stress, which in turn oxidises pre-existing melanin. This leads to rapid darkening of already existing melanin. Secondly, there is an increased production of melanin (melanogenesis).[1] It is a reaction of the body to photodamage from UVB.[2] Melanogenesis leads to delayed tanning. It first becomes visible about 72 hours after exposure.[1] The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin.
Darkening of the skin is caused by an increased release of the pigment melanin into the skin's cells after exposure to ultraviolet radiation. Melanin is produced by cells called melanocytes and protects the body from direct and indirect DNA damage absorbing an excess of solar radiation, which can otherwise be harmful. Depending on a person's genetic profile, some people can darken quickly and deeply whereas others do not darken much at all.
The ultraviolet frequencies responsible for tanning are often divided into the UVA and UVB ranges.
UVB
Ultraviolet B radiation is in the wavelength range 280 to 320 nm.
• triggers the formation of CPD-DNA damage (direct DNA damage) which in turn induces an increased melanin production[2]
• is more likely to cause a sunburn than UVA as a result of overexposure. The mechanism for sunburn and increased melanogenesis is identical.[3] Both are caused by the direct DNA damage (formation of CPDs)
• reduced by virtually all sunscreens in accordance with their SPF
• is thought to cause the formation of moles and some types of skin cancer
• causes skin aging (but at a far slower rate than UVA.)
• produces Vitamin D in human skin
UVA
Ultraviolet A radiation is in the wavelength range 320 to 400 nm. It is present more uniformly throughout the day, and throughout the seasons than UVB. UVA causes the release of preexisting melanin from the melanocytes to combine with oxygen (oxidize), which in turn creates the actual tan color in the skin. UVA seems to cause cancer less than UVB, but causes melanoma, a far more dangerous type of skin cancer than other types. It is blocked less than UVB by many sunscreens but is blocked to some degree by clothing. When tanning in a tanning bed that mainly produces UVA rays the tan goes deeper into the skin as well as lasting longer which allows the tanner to keep the desired color with fewer visits.
Cultural history
A man sunbathing




Throughout history, tanning has seen several fluctuations in popularity. In early civilizations with a class system, social distinctions existed between those of tanned complexion and those without. This class system often separated those deemed to be high class and those who were not. This distinction was physically manifested in the color of one’s skin. Those who often spent long hours working in the sun were often grouped together as lower class.[4] Women even went as far as to put lead-based cosmetics on their skin to artificially augment their appearance.[5] However, these cosmetics slowly caused their death through lead poisoning. Achieving this light-skinned appearance was brought about in many other ways, including the use of arsenic to whiten skin, on to more modern methods such as full length clothes, powders, and parasols. This fair-skinned trend continued up until the end of the Victorian era. Niels Finsen was awarded the Nobel Prize in medicine in 1903 for his “Finsen Light Therapy”.[6] This therapy was to cure infectious diseases such as lupus vulgaris and rickets. Vitamin D deficiency was found to be a cause of rickets disease, and exposure to the sun would allow Vitamin D to be produced in a person. Therefore, sun exposure was a remedy to curing several diseases, especially rickets. Shortly thereafter, in the 1920s, Coco Chanel accidentally got sunburnt while visiting the French Riviera. 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. Those who liked and idolized her wanted darker skin so they could be more like her. These two French women were two trendsetters of the transformation of tanned skin being viewed as fashionable, healthy, and luxurious.[7][8][9]
In the 1940s, women’s magazines started using advertisements that encouraged sun bathing. At this time, swimsuit's skin coverage began decreasing and tanning oil came out. The bikini made its appearance in 1946. Louis Reard was the French designer who introduced the bikini. In the 1950s, an ever-growing trend was to use baby oil as a method to tan more quickly. The first self-tanner came about in the same decade and was known as “Man-Tan,” and often led to undesirable orange skin.[5] Coppertone, in 1953, brought out the little blond girl and her cocker spaniel tugging on her bathing suit bottoms on the cover of their sunscreen bottles; this is still the same advertisement they use today on their bottles of sunscreen. In the latter part of the 1950s, silver metallic UV reflectors were common to enhance one’s tan. In 1971, Mattel introduced Malibu Barbie, which had tanned skin, sunglasses, and her very own bottle of sun tanning lotion. The same decade, specifically 1978, gave rise to tanning beds and sunscreen with SPF 15. Today there are an estimated 50,000 outlets for tanning, whereas in the 1990s there were only around 10,000.[10] The tanning business is a five-billion dollar industry.[10] In some other parts of the world, fair skin remains the standard of beauty. The geisha of Japan were renowned for their brilliant white painted faces, and the appeal of the bihaku (美白?), or "beautiful white", ideal leads many Japanese women to avoid any form of tanning.[11] There are exceptions to this, of course, with Japanese fashion trends such as ganguro emphasizing almost black skin. The color white is associated with purity and divinity in many Eastern religions. In India, dark skin is heavily associated with a lower class status, and some people resort to skin bleaching to achieve a skin color they view as more socially acceptable.
Sociological perspective
According to several studies, both men and women view a tanned body as more healthy than a pale body,[13] even though tanning sometimes leads to an unhealthy body by way of blistered or burnt skin, wrinkles, and skin cancer. This represents a conflict between one’s health and the social values of being perceived as healthy or physically attractive. Some people prefer to appear healthy and conform to society’s expectations, rather than curtail risk by avoiding sun damage.[14] The image one conveys through having bronzed skin is largely responsible for the ever-growing trend of tanning today.[14]
Tanning controversy
More recently, some researchers have advised that tanning in moderation may be healthier than is commonly believed. Edward Giovannucci, professor of medicine and nutrition at Harvard states that according to his research, people who have sufficient vitamin D due to UV exposure, and other intake, may prevent 30 deaths for each one caused by skin cancer.[15] His research also suggests that diet accounts very little for vitamin D-3 necessary for curbing cancer. Michael Holick, Boston professor of dermatology, claimed that moderate exposure to sunlight probably reduces risk to many forms of cancer, diabetes, seasonal affective disorder, and other diseases.[16] These researchers are vigorously opposed by most dermatologists, for example, Dr. Elewski, president of the American Academy of Dermatology, argued that minutes of exposure to sunlight can be dangerous, and that people can get all the vitamin D they need through supplements. Large clinical studies have found vitamin D produced both through exposure to sunlight and through dietary supplements dramatically decreases cancer risk, and helps cancer recovery. See Vitamin D for more details.
Dressing for tanning
To maximize tan coverage, some people minimize the amount of clothing they wear while tanning. Depending on local community standards and personal choice, some people suntan without clothes, while others suntan topless, and others wear very brief swim wear, such as a microkini. Some people suntan in the privacy of their back yard, where they can at times wear what they choose, and some countries have set aside clothing-optional beaches (also known as naturist, nude or nudist beaches), where Excessive exposure to direct sunlight is considered potentially harmful to a person's health. To avoid sunburn a person should stay out of the sun for long periods of time. If long sun exposure cannot be avoided or is desired one may cover themselves or use sunscreen or various over-the-counter creams to reduce the risks from UVA and UVB exposure. The SPF (Sun Protection Factor) number on a sunscreen product shows its rated effectiveness. Products with a higher SPF number provide greater protection against ultraviolet radiation. However in 1998, the Annual Meeting of the American Association for the Advancement of Science reported that some sunscreens advertising UVA and UVB protection do not provide adequate safety from UVA radiation and could give sun tanners a false sense of protection.

For those who choose to tan, some dermatologists recommend the following preventative measures:

Make sure the sunscreen blocks both UVA and UVB rays. These types of sunscreens, called broad-spectrum sunscreens, contain more active ingredients. Ideally a sunscreen should also be hypoallergenic and noncomedogenic so it doesn't cause a rash or clog the pores, which can cause acne.
Sunscreen needs to be applied thickly enough to make a difference. People often do not put on enough sunscreen to get the full SPF protection. In case of uncertainty about how much product to use, or discomfort with the amount applied, switching to a sunscreen with a higher SPF may help.
Research has shown that the best protection is achieved by application 15 to 30 minutes before exposure, followed by one reapplication 15 to 30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, and rubbing.[17]
The rays of the sun are strongest between 10 a.m. and 4 p.m,[18] so frequent shade breaks are recommended during these hours. Sun rays are stronger at higher elevations (mountains) and lower latitudes (near the equator). One way to deal with time zones, daylight saving time (summer time) and latitude is to check shadow length. If a person's shadow is shorter than their actual height while standing, the risk of sunburn is much higher.
Wear a hat with a brim and anti-UV sunglasses, which can provide almost 100% protection against ultraviolet radiation entering the eyes.
Be aware that reflective surfaces like snow and water can greatly increase the amount of UV radiation to which the skin is exposed.
The American Academy of Dermatology recommends the use of sunscreens, wearing sun protective clothing and avoiding the sun altogether.

Recent evidence indicates that caffeine and caffeine sodium benzoate increase UVB-induced apoptosis both in topical and oral applications. In mice, UVB-induced hyperplasia was greatly reduced with administration of these substances. Although studies in humans remain untested, caffeine and caffeine sodium benzoate may be novel inhibitors of skin cancer.[19]

Tanning and sunscreen
In his book Physician's guide to sunscreens Nicholas J. Lowe pointed out, that one of the reasons for customers to reject sunscreen use is the reduction of tanning that is associated with good sunscreen protection.(chapter 7 page 81)[20] He then reports about several tanning activators. The specific substances which he writes about are different forms of Psoralen. These substances were known to be photocarcinogenic since 1979.[21][22][23] Despite the obvious photocarcinogenic effects the authorities disallowed Psoralen