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SCIENCE: The Causes & Effects of a Suntan

 

As most people know a suntan is caused by exposure to UV rays. That is a simple fact but the rest of the story is more complicated. The ease with which a person may suntan and the health concerns related to time spent in the sun differ based on skin type and the type of ray that is stronger on any given day.

 

First let us look at your skin to better understand what happens. Your skin is the largest organ in your body and also the most versatile. Just think!  Your skin is responsible for holding everything else together. From head to toe it protects all the muscles, bones and every other organ. What does it protect them from?  Sun, injury, variance of air temperature, and infection come to mind immediately. In addition it has the job of storing body fat, producing vitamin D and regulating body temperature. Skin is made up of three layers known as the epidermis, dermis and subcutis.

 

The epidermis is the outer layer and is made up of squamous cells, which sit on basal cells which are layered over melanocytes. Melanocytes are the cells that produce melanin which causes them to darken as the first defense against sun damage. The dermis is comprised of blood vessels, lymphatic vessels, hair follicles and glands which work together to protect the epidermis from air temperature changes and drying out. The subcutis layer is defense for the other organs.

 

Two different types of UV rays are responsible for skin change, UVA (NUV) with a wavelength of 320 to 400 nm wavelength and UVB (FUV) whose wavelength is 280 to 320 nm. The response to both types is a rallying of the troops in the form of melanin production.  Melanin is what is responsible for your skin color. It is a dark brown protective pigment which is produced in response to the UV rays contact with skin. Individuals, who already have an abundance of melanin on the surface, as in darker skinned people, will still need to use protection. Both UV types are responsible for tanning with UVA tending to cause wrinkles, liver spots, loss of elasticity, premature aging and cataracts, while UVB is the culprit which causes sunburn. Both types are responsible for skin cancers of varying types. The type of ray that most often reaches earth is the UVA while UVB is filtered by ozone and oxygen.

 

UVB rays penetrate to the epidermis while UVA rays penetrate the thicker, deeper levels of dermis and subcutis.  Upon penetration, the shorter wavelength of UVB can cause greater biological effects in cells. UVA is responsible for the suppression of the immune system which allows the formation and spread of skin cancer cells. This can lead to the less prevalent but more dangerous type of skin cancer, malignant melanoma. The result of excessive UVB exposure can be indirect DNA damage which can lead to the less dangerous but more prevalent types of skin cancer, basal cell carcinoma and squamous cell carcinoma. Remember these cells make up the top two levels of the epidermis. Excessive exposure to UVB will induce direct DNA damage which can then result in sunburn which increases the probability of skin cancer.

 

It is the epidermis reaction and the melanin response to the two different types of rays that will dictate how quickly you tan, how well you tan and whether you leave with sunburn.

 

-Suntanwomen

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