Skin tanning

Canthaxanthin, cutaneous malignant melanoma, dermis, DHA, dihydroxyactone, epidermis, indoor tanning, melanocytes, melanoma, outdoor tanning, sunless tanning, tanning lotion, tanning oils, tanning pills, UVA, UVB, UVR, UV radiation.

Tanning is a process in which skin pigmentation darkens as a result of exposure to ultraviolet light. There are two types of skin tanning. Immediate tanning is a response to the UVA radiation of sunlight. This tanning arises just a short time after sunbathing and lasts only a few hours or days. Delayed tanning is caused by the UVB radiation of sunlight. It appears approximately 2-3 days after sunbathing and lasts longer, disappearing with natural renewal of the skin. The intensity of tanning depends on the skin type.

Many Americans, including up to 80% of people under age 25, believe they look better with a tan. But this infatuation with tanning only came about in the 20th Century. In the 19th Century and earlier, being as pale as possible was desirable in certain countries, particularly the United States and some European nations. Being pale was a symbol of wealth. Now, in the 21st Century, tanning is very popular. Indoor tanning, one of the most popular types of tanning, is reported to be a $2 billion-a-year industry in the United States. According to industry estimates, 28 million Americans are tanning indoors annually at about 25,000 tanning salons around the country. There are several types of popular tanning methods.

Outdoor tanning is tanning from the direct exposure to sunlight. Many forms of outdoor tanning products are available, including creams, gels, sprays, and lotions.

Indoor tanning is tanning without the direct exposure to sunlight. Some of the devices used for indoor tanning are tanning beds and sunlamps. Other tanning devices are tanning "accelerators" or tanning pills. These products claim to speed up the body's production of melanin or darken the skin, but there is currently no evidence that these products are effective and they have not been approved by government agencies for tanning purposes. Most sun lamps and sun beds emit mainly UVA radiation and are less likely to cause sunburn than UVB radiation from sunlight. But, contrary to the claims of indoor tanning being safe, some tanning lamps do emit UVB light as well and also the concentration of UVA light from a tanning bed is far greater than that from the sun, some reports state that it is about 5 times greater than from the sun, so in the long run a person may absorb more rays, and increase the risk for skin cancer and other side effects. There has been a suspected link between malignant melanoma and UVA radiation as well as UVB radiation.

Sunless tanning is tanning without any UV exposure. It works by oxidation of the outermost skin by dihydroxyactone (DHA). DHA is the only color additive approved by the Food and Drug Administration (FDA) for use in sunless tanning products. When applied, DHA reacts with dead cells in the outermost layer of skin (stratum corneum) to temporarily darken the skin's appearance within two hours. The coloring does not wash off, but it gradually fades as the dead skin cells slough off. In most cases, the color is completely gone after five to seven days. There are many different forms of sunless tanning products available for home use, and spray-on tanning available at salon. These professional applications can provide an even, full-body tan.

Skin is the largest organ and the main barrier between the body and the environment. It also contains cells that help immune system fight off infections.

A small amount of sunlight is needed for the body to produce vitamin D. Vitamin D together with calcium is known to protect against bone disease including osteoporosis and osteomalacia in adults. However, it does not take much sunlight to make all the vitamin D one can use, certainly far less than it takes to get a suntan.

The sun's rays contain two types of ultraviolet radiation that reach the skin: UVA and UVB. The third type is UVC, but it is absorbed by the earth's atmosphere before it reaches humans. UVB radiation burns the upper layers of skin (the epidermis), causing sunburns, whereas UVA radiation, which penetrates to the lower layers (the dermis), causes tanning. UVA rays are considered the culprit in the aging of skin, and UVB rays are more often linked to skin cancer. However, research suggests that UVA radiation may also play a role in skin cancer.

A tan is visible proof that the skin is being damaged. When ultraviolet radiation hits the skin, it stimulates cells known as melanocytes, which make a brown pigment called melanin. The melanocytes respond to the sun by making even more melanin to protect the skin from the sun. The melanin acts like an umbrella for the skin's cells and can give people the brown tint that is a suntan.

Different people have different amounts of melanin in their skin. Those with a Northern European background tend to have less melanin and are rather pale, whereas people with dark brown skin have more melanin. Based on these differences, dermatologists have come up with six skin types, ranging from a Type I (fair skin, blonde or red hair, and always burns in the sun) to a Type VI (black skin and usually does not get sunburned). People who are a Type V or VI have more natural protection against the sun than those who are a Type I or II, but that does not mean they should ignore warnings about sun exposure.

Epidemiologic, clinical, and laboratory studies have supported a causal role of the ultraviolet portion of the sun's rays in the development of skin cancer. UV radiation seems to be the cause of all three common skin cancers -- basal cell carcinoma, squamous cell carcinoma, and melanoma. It is thought to induce skin cancers by three mechanisms: First, ultraviolet light directly damages DNA leading to mutations; second, it produces activated oxygen molecules that in turn damage DNA and other cellular structures; and third, it leads to a localized immunosuppression, thus blocking the body's natural anti-cancer defenses.

Solar UV radiation exposure is estimated to account for over 90% of melanomas in North America, and Australia, with similar figures for Northern Europe. Over the past 25 years, a number of case-control and cohort studies have addressed the relationship of cutaneous malignant melanoma with solar UV radiation. Overall, the results indicate that intermittent solar exposure is strongly associated with an increased risk of melanoma. Total or cumulative exposure appears to be weakly related to risk, although a greater effect for cumulative exposure might have been missed in many studies due to limited range of exposure. The results also suggest that early life exposure may be important in relation to later risk of cutaneous malignant melanoma.

Ten studies provided data for assessment of melanoma risk among subjects who reported "ever" being exposed compared with those "never" exposed to indoor tanning. A positive association was found between exposure and risk (summary OR, 1.25; 95% CI, 1.05-1.49). Significant heterogeneity between studies was present. Evaluation of the metrics "first exposure as a young adult" (5 studies) and "longest duration or highest frequency of exposure" (6 studies) also yielded significantly elevated risk estimates (summary OR, 1.69; 95% CI, 1.32-2.18, and 1.61; 95% CI, 1.21-2.12, respectively, with no heterogeneity in either analysis). The results from these ten studies indicate a significantly increased risk of cutaneous melanoma subsequent to sunbed/sunlamp exposure.

A case report of 39 year-old patient with a previous history of melanoma reported a development of three primary melanomas within a few years of initiating tanning bed. The case report concluded that intense UV exposure likely contributed to the development of additional primary melanomas especially in the individuals with an increased risk of skin cancer.

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

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