Wax bloom is a white haze that appears on colored pencil drawings with certain wax-based pencils. It occurs as the wax rises to the surface of the work. It especially happens when the wax-based pencils are heavily worked. It usually appears after the work has been sitting a week or so, but can sometimes occur the same day.
To remove wax bloom, a soft cloth (or cotton swab for smaller areas) lightly rubbed in the area will work. Do not apply too much pressure as you can lift pigment. To prevent further bloom, a fixative can be used.