Sun and Sunless Tanning

Sun tanning
A darkening of the skin, generally of those having fair-skin, after exposure to ultraviolet radiation of sunshine or sunbed is called "Sun tanning".

Mechanism of Sun tanning
The ultraviolet radiation stimulates a natural physiological response that leads to the darkening. During exposure to ultraviolet radiation, the pigment melanin is produced in cells called melanocytes. The melanin is released into the skin's cells and this darkens the skin. It also protects the body from absorbing an excess of solar radiation. As per the genetic constitution, some individuals darken fast while others do not darken at all.

The UVA and UVB rays are responsible for tanning. The latter have more energy than the former and can effect more damage. The UVB rays:

• foment creation and secretion of new melanin into the skin
• are more carcinogenic than UVA rays
• create Vitamin D in the human skin
• are decreased by nearly all sunscreens as per their SPF
• lead to skin aging, but at a slower rate than UVA rays
• may lead to a sunburn due to overexposure

The UVA rays:

• release the pre-existing melanin from the melanocytes
• lead to the oxidization of melanin and this creates the tan color in the skin
• cause melanoma, a very dangerous skin cancer
• are present more uniformly all over the day and in all seasons as compared to UVB
• are blocked somewhat by clothing and to a lesser degree by sunscreens than UVB

Benefits

• as sun exposure causes Vitamin D production, this is essential for those with Vitamin D deficiency. It is analyzed that 50,000 to 63,000 deaths occur yearly in the United States due to insufficient Vitamin D. Scarcity of this vitamin can also lead to bone pain, difficulty in weight bearing and at times fracture
• skin conditions like psoriasis and vitiligo can be treated
• sun exposure in childhood results in prevention of multiple sclerosis in adulthood
• acne can be hidden or treated if there is short-term sun exposure

Hazards

• overexposure may lead to sunburns and melanoma
• in the southern hemisphere, as the ozone layer has been depleted, dangerously high levels of UV radiation enter the earth's atmosphere increasing the incidence and severity of sunburn
• UV light causes the production of endorphins which results in a natural feeling of well-being. In this way, indoor sun tanning can be addictive
• the immune system and eyes may be damaged by overexposure

Sunless tanning
Application of chemicals on the skin to result in an appearance similar to sun tanning is called "Sunless" or "Self" or "UV-free" tanning. The most efficient chemicals are those containing dihydroxyacetone (DHA). Products containing the amino acid tyrosine are also used as tanning accelerators. Canthaxanthin is a color additive used in some foods. Melanotan hormone is a melanocyte-stimulating hormone that is another choice. Bronzers are temporary sunless tanning options.

Mechanism of Sunless tanning
A chemical reaction takes place between the DHA and the amino acids present in the dead layer on the skin surface. This is totally non-toxic as well as skin safe and the damage linked with UV exposure is absent. The tan produced is impermanent and fades in 3 to 10 days. If Erythrulose is mixed with DHA, a longer lasting sunless tan can be made. Products containing tyrosine are said to increase melanin formation, but they require UV exposure. Also, this claim is not backed by scientific data. After consumption of canthaxanthin, it gets deposited all over the body and consequently also in the layer of fat below the skin. This gives the skin an orange-brown hue. Melanotan also requires UV exposure to be effective. Bronzers create a tan that can be easily removed with soap and water.

Procedure

• wash the skin and peel off excess dead skin cells. Women should shave their legs
• choose a light or medium-colored product as it is more natural
• apply the product evenly and lightly. Less product must be applied on dry or thickened skin like knees, ankles and elbows
• wash hands with soap and water thereby avoiding coloring of the hands. Use a cotton ball to apply the product to the top of the hand
• wait for 15 to 20 minutes till the sunless tanner dries. Then, wear clothes

Hazards

• DHA or Erythrulose may lead to contact dermatitis
• Canthaxanthin may result in hepatitis and canthaxanthin retinopathy in which yellow deposits are formed in the retina of the eye. The digestive system may also be damaged
• Bronzers have less sweat or light water resistance. They lead to some rub-off on tight clothes