Whether patients with mouth ulcers will be infected with hepatitis B generally depends on the severity of mouth ulcers and whether they have been injected with hepatitis B vaccine and other factors. 1. Mouth ulcers will not be infected with hepatitis B: under normal circumstances, mouth ulcers with mild symptoms, local bleeding phenomenon, or have been injected with hepatitis B vaccine, the body has produced protective antibodies, i.e., hepatitis B surface antibodies, generally will not be infected. 2. Mouth ulcer patients will be infected with hepatitis B: generally deeper ulcers and bleeding, hepatitis B patients with high levels of hepatitis B virus in the body, in the depth of kissing or eating with the same meal happens to be also a broken mouth blood exposure, the infected person’s body without hepatitis B antibody or antibody titer is very low, then may be infected with hepatitis B. Oral ulcer patients and hepatitis B patients should pay attention to protection, avoid close contact, blood, body fluids exposure, timely injection of hepatitis B vaccine to reduce the chances of being infected.