UV effects: Long exposure to the sun may inflame skin and cause it to swell. Even longer exposure results in burning, with blistering and peeling, and possibly heatstroke, which causes the temperature-regulating mechanism of body to give up.

The effects of too much UVA exposure may also lead to eye damage, immune system changes, cataracts, wrinkles and premature aging of the skin.

Precautions: Caution is advised in those who have fair skin; have blonde, red, or light brown hair; have blue, green, or gray eyes; always burn before tanning; burn easily; do not tan easily, but spend a lot of time outdoors; have previously been treated for skin cancer or who have a family history of skin cancer; live in or take regular vacations to high altitudes (ultraviolet exposure increases with altitude).

The sun's rays are strongest between 10:00 AM and 4:00 PM, and direct long-term exposure is not advised during those hours. Reflective surfaces like snow and water may increase the amount of UV radiation to which an individual's skin is exposed.

Hats with a brim, and sunglasses, may help protect against the sun outdoors. Protective goggles, available at the tanning salon, are recommended for use with indoor tanning, as the eyes can be severely burned by the intense UV rays emitted by the light source.

Many dermatologists recommend avoiding continued use of a tanning bed or sunlamp particularly during the teen-age years due to a greater risk for skin cell damage because of rapidly dividing skin cells.

Sunscreen is also recommended for protection and is regulated by the Food and Drug Administration (FDA) as an over-the-counter (OTC) drug. Cosmetics that make sun-protection claims are regulated as both drugs and cosmetics. Most experts recommend a sun protection factor (SPF) of 15 or more. The higher the number, the better the protection. Sunscreen should be liberally applied to skin 30 minutes before going out in the sun, and then every two hours after that. Sunscreens that block both UVA and UVB rays (broad-spectrum sunscreens), hypoallergenic and non-comedogenic are recommended by most experts.

Dihydroxyactone (DHA): Dihydroxyactone (DHA) has been approved by the FDA for use as a tanner since 1977, and has typically been used in OTC lotions and creams. Its use is restricted to external application, which means that it should not be sprayed in or on the mouth, eyes, or nose. During the last few years, some companies have offered a sunless option that involves spraying customers in a tanning booth with the color additive DHA.

Tanning pills: There are no tanning pills approved by the FDA. Some companies have marketed tanning pills that contain the color additive canthaxanthin. When large amounts of canthaxanthin are ingested, the substance can turn the skin a range of colors, from orange to brown. The additive is not listed for use in tanning pills in the United States, but rather is approved for use as a food color additive, and only in small amounts. Imported tanning pills that contain canthaxanthin may be refused entry into the United States because they contain non-permitted color additives.

Tanning pills have been associated with health problems, including an eye disorder called canthaxanthin retinopathy, which is the formation of yellow deposits on the eye's retina. Canthaxanthin has also been reported to cause liver injury and a severe itching condition called urticaria.

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.