Pigmentation is the coloring of a person’s skin.
When a person is healthy, his or her skin color will appear normal.
In the case of illness or injury, the person’s skin may change color, becoming darker (hyperpigmentation) or lighter (hypopigmentation).
hypopigmentation in skin is the result of a reduction in melanin production. Examples of hypopigmentation include:
simple causes like pityriasis alba, pityriasis versicolor, dryness of skin, after healing of rash like eczema, overuse of topical steroid cream etc to serious causes like leprosy or skin cancer too.
Not every white patch is vitiligo.
Calcium deficiency is not the reason for white patches on face
To know the correct diagnosis of white patch on your body and for proper treatment consult a MD dermatologist.
Readmore:
http://www.webmd.com/skin-problems-and-treatments/hyperpigmentation-hypopigmentation#1
http://www.medscape.org/viewarticle/739758_7
