Vitiligo

Pigmentation means the process of skin which is responsible for the coloration of skin.  It is also related to the mechanism of skin regarding absorption of heat coming from sunlight. It protect our body from hazardous rays of uvb light which interact with our body. UVB light  is a big source of skin cancer.

Skin color is the one of the most important factor by which you guesses overall health condition of a person. There is direct effect on the skin or the pigmentation of skin due to any unwanted change or weakness in one's body system. Some time the lack of some nutrients like vitamins and mineral causes some problems in the pigmentation process of skin. And some time anomalies in the internal system (auto-immune system of body) may results the some unwanted spots in the skin. There are many skin pigmentation problems but here we shall discuss some main thing regarding the skin appearance. Before continuing further first we have to explore the term melanin.

Melanocytes

Melanocytes are special skin cell which are responsible for pigmentation process of skin.
 
Melanin

A natural substance produced by pigmentation producing cells melanocytes which is responsible for natural skin and hair color.
It is the melanin which deficiency or excess in skin causes different types of skin problem. Albinism and vitiligo occurs due to the deficiency of melanin in skin.
Abnormalities in the function in the production of melanin by melanocytes  cause different pigmentation problems in skin.
Melanin has a special quality to absorb UV (ultra violet) radiation from sun.

Hyper Pigmentation

It occurs when the production of melanin substance increase  from normal level. Normally dark spots or blotches on skin occurs due to the hype-pigmentation.
You may often observe that after tannin or long being long exposure to sun your skin complexion become more darken. This happens due to the excessive of melanin.
Liver spots is the most common hyper-pigmentation disorder. It occurs due to the pro long exposure to the sun.

Depigmentation

It is also called hypo-pigmentation. When some light spots appear in skin as compare to its surrounding, normally white patches in skin appear due the depigmentation in skin. It occurs when the amount of melanin decrease from a certain level in a particular part of the body.
Most common depigmentation problem of the skin is vitiligo.  About 50 million people on the globe ar suffering from this skin condition.  Vitiligo occurs due to the destruction of the pigment producing cells of skin and lack of melanin.
Some hyper-pigmentation techniques are also used for treatment of vitiligo.
You can visit for further info about other depigmentation conditions.


Ultra Violet Radiation

Here is need to mention some thing about ultra violet radiation because most of the pigmentation problems, specially hyper-pigmentation occur due to the  uv light.
Special pigment material melanin has a quality to absorb uvb radiation. Though UV light therapy is also used for the treatment of many disease. Rapid increase in using sunscreens in last few year is also has been observed is also due to the uv rays.

Some Useful tips to save your skin

Drink more water.
Take care white going out, specially extreme sun hours.
Use Sunscreen but made of safe substance instead of toxic chemical materials.

source: http://www.vitiligoguide.com/white-spots-on-skin/