The human skin contains melanocytes; special cells located in the bottom layer of skin's epidermis. The melanocytes produce the melanin pigment which gives color to the skin through the process called melanogenesis. The amount of melanin produced by the body determines the skin color of a person. The production of melanin depends upon race and environmental factors.
The melanocytes are present in the mucous membranes (the tissues that line the inside of the nose, mouth and genital areas), hair and the retina of the eyes. When Vitiligo occurs the melanocytes are either destroyed or damaged. These melanocytes are unable to produce enough amount of melanin required by the body. The area deficient of melanin turns white. Therefore, white patches of skin appear on different parts of the body. Sometimes retina and the inside of the mouth are also affected by Vitiligo. Also the hair that grows in areas affected by Vitiligo may turn white.