It is possible that the ulcer surface becomes red because the ulcer is close to healing, or it is possible that the surrounding tissues and submucosal tissues have an inflammatory reaction of congestion, redness and swelling, and the specific situation should be analyzed. Oral ulcers are relatively common in daily life and are not taken seriously because they can recur or heal naturally after a period of time. During the onset of ulcers usually need to go through the stages of ulcer epithelial breakage, ulcer epithelial surface covered with pseudomembrane, and ulcer epithelial with granulation growth. If the ulcer is in the granulation stage, the ulcer will become red, but its surface will be smooth, and the burning pain will be reduced. If the ulcer surface becomes red, but the base becomes hard or the burning pain increases, it usually means that there is a bacterial infection around the ulcer, and this situation needs to be treated with oral cephalosporin anti-inflammatory drugs, such as cefprozil capsules.