Recurrent mouth ulcers are the most common oral mucosal disease and can affect people of different genders, ages, races, and geographic areas. Mouth ulcers after transplantation are also common. For the general population the incidence of recurrent oral ulcers can be as high as 20%, and there are no relevant statistics for transplant patients. The etiology of recurrent oral ulcers is unclear and may be related to local trauma, stress, diet, medications, hormones, and vitamin and micronutrient deficiencies. For post-transplant patients, in addition to the above etiologies, anti-rejection drug-related oral ulcers are the most common, such as rapamycin (especially at higher concentrations) and mycophenolate, which are prone to induce oral ulcers and are frequently seen in clinical practice. The above etiologies have often been reported more in the literature, but there are no effective methods to eradicate recurrent oral ulcers, which are often treated symptomatically during the onset of oral ulcers and may develop again later after remission. In recent years, there have been some new in-depth studies on its etiology that may be helpful in suppressing its recurrent attacks. For example, much of the existing literature suggests a correlation between H. pylori and recurrent oral ulcers. The presence of many colonizing bacteria in the oral cavity, the ecological characteristics of the oral plaque, the suitable temperature of the oral cavity, and the fermentation and acid production of bacteria in the plaque are all conducive to the parasitization of H. pylori in the oral cavity, and H. pylori itself has a strong ability to adhere, especially through the action of adhesins such as salivary acid-specific hemagglutinin, which subsequently leads to ulceration through the following mechanisms: mucosal autoantigens → sensitization lymphocyte antibodies → initial mucosal damage induced by sensitized lymphocyte antibodies → immune complexes → local activation of complement → cytolysis → polymorphonuclear cell infiltration → inflammation → focal mucosal damage → ulcer formation. In addition, in recent years, it has been suggested that the microecology of the intestine plays an important role in the pathogenesis of oral ulcers, and regulating the intestinal microecology and correcting the imbalance of intestinal flora are useful in reducing H. pylori infection, improving allergic diseases, promoting the synthesis of multiple vitamins and biological enzymes, increasing the absorption of trace elements, and also reducing the absorption of toxins in the digestive tract, thus inhibiting the inflammatory lesions of organs and oral ulcers. It also reduces the absorption of toxins in the digestive tract, thus inhibiting the inflammatory lesions of organs and the frequent occurrence of mouth ulcers. What is the treatment plan for recurrent mouth ulcers in transplant patients? First of all, it is important to clarify whether the onset of mouth ulcers is related to immunosuppressive drugs (rapamycin, mycophenolate). If frequent mouth ulcers occur after adding this drug, then it is necessary to decide whether to reduce or stop the drug according to the degree of mouth ulcers, and the specific implementation of the reduction or discontinuation should be contacted to your follow-up physician, and should not be adjusted without permission to avoid causing abnormalities in the function of the transplanted organ. In addition, supplementation of vitamins and trace elements, 21 gold vitamins, and Sun Cun are available. Most studies have found that supplementation of the above-mentioned agents is effective, in addition, vitamin B2 and vitamin C alone, are also clinically observed to be effective. Third, local symptomatic treatment, oral ulcer film, some oral specialist hospital developed oral ulcer dispersion, not only inexpensive, and to promote ulcer healing, reduce local pain, very effective, local medication for transplant patients is also safe. In addition, for patients with large ulcers, it is also recommended to add topical medication to facilitate ulcer healing. Finally, supplementation of intestinal probiotics and regulation of intestinal microecology. In recent years, more and more scholars have suggested that long-term supplementation of intestinal probiotics and regulation of intestinal microecology are beneficial for the treatment of mouth ulcers and prevention of recurrent mouth ulcers. Bifidobacterium, Bacillus subtilis and Bacillus licheniformis are optional, swallowed with warm water half an hour after three meals, two capsules each time.