I am treating my allergy from benzoyl peroxide the red areas are becoming brownish in color and looks like a crust on skin is it scarring or healing?

Hard to say. Apply Vaseline to those areas twice a day for 1 week. After that time the skin should be smooth even though it may be brown. At that point I would wear a sunscreen all the time to help the brown discoloration fade. You can also speak to a doctor regarding the use of a hydroquinone or other bleaching cream. You probably did not get a scar.