Oral ulcers white after healing may be pseudomembrane or scarring, both of which are normal, as follows. 1. Pseudomembrane: it is a mixture of inflammatory exudate, inflammatory cells, fibrin, necrotic epithelial cells and tissues, covering the surface of the lesion, which can protect the wound and promote wound healing. It will be gradually replaced by normal oral mucosa. 2. Scarring: larger and deeper ulcers may show scarring after healing, which will become softer and lighter in color over time, and then gradually disappear. There may be other reasons for the whitening of mouth ulcers after healing, if the symptoms do not improve or other symptoms occur, it is recommended to go to the hospital in time, after a clear diagnosis for targeted treatment.