White spots on the skin, also known as hypopigmentation, is the loss of pigment in the skin resulting in greater whiteness than in the surrounding area. As melanin pigment is not produced in an area of the skin, the affected area losses color.

There are a number of things that may cause this spotting:

Skin Damage:

skin infections, lasers inappropriately applied, burns or blisters, or other forms of skin trauma may result in hypopigmentation and a loss of color in the skin

Albinism:

Albinism is a genetic disorder passed onto children from their parents. Melanin is not produced in people who have albinism resulting in a total absence of pigment in the skin, hair or eyes. People with albinism are at serious risk for sun damage and skin cancer and as such should be sure to wear sunblock at all times.

Vitiligo:

Vitiligo is a chronic skin disorder resulting in large, irregular discolored patches on the skin. Most of the affected areas lose pigment, though pigment may come back as melanin is reproduced in the affected areas.