A swollen face from a mouth ulcer is likely to be caused by a concurrent bacterial infection. Mouth ulcers are painful sores that appear inside the mouth and can cause painful and uncomfortable symptoms, which normally do not cause symptoms of a swollen face. However, if the mouth ulcers are severe, such as large and deep ulcers, when the patient does not pay attention to oral hygiene, it is likely to cause interstitial infections, resulting in swelling of the face, and there may be fever, lymph node swelling and other symptoms. It is recommended that people with swollen faces due to mouth ulcers go to a regular hospital in a timely manner to clarify the cause and standardize the treatment under the guidance of the doctor, so as not to delay the condition to bring adverse effects on the body and add an extra burden to the body.