There is no such thing as the fastest treatment for mouth ulcers during breastfeeding, you should choose the appropriate treatment according to the cause of the disease. Possible causes include recurrent mouth ulcers, immune system diseases, cancerous ulcers and so on, which can be treated with medication, surgery and so on. 1. Recurrent oral ulcers: generally oral ulcers are recurrent oral ulcers, which can be healed in 10 days or so, and can also be treated with recombinant human epidermal growth factor gel and other drugs. 2. Immune system diseases: If mouth ulcers recur frequently, they may be caused by immune system diseases such as systemic lupus erythematosus, at this time, it may be necessary to suspend breastfeeding, oral celecoxib and other non-steroidal anti-inflammatory drugs for treatment, as well as oral glucocorticoids and other medications to control the activity of lupus. 3. Cancerous ulcers: If the ulcers are deep and large and last for a long time, they may be malignant ulcers, such as oral cancer, etc. At this time, it may be necessary to suspend breastfeeding and undergo surgery or radiotherapy. All of the above medications should be used under the guidance of a doctor. If the mouth ulcers are serious or have not healed in more than 2 weeks, you should go to the hospital in time to find out the cause and carry out targeted treatment.