Vitiligo is one condition that can cause white spots on the back and neck, according to WebMD. The condition occurs when the body destroys the cells that are responsible for color pigment in the skin.
The condition can affect any part of the body and the exact cause is unknown. There is no cure for vitiligo, but cosmetic procedures and corticosteroid creams can reduce the appearance of the white spots.
Folliculitis can also cause white spots as stated by Mayo Clinic. This condition occurs when the hair follicles become infected. It is most common after a person shaves and it is treated with antibiotic skin creams.