A bag growing inside the mouth may be caused by mucous gland cysts, oral ulcers, herpes and boils. 1. Mucous gland cyst: this disease is mainly caused by local trauma and obstruction of the ductal system, resulting in patients with a bag inside the mouth, accompanied by swallowing, breathing difficulties and other symptoms. 2. Mouth ulcers: if affected by infection, endocrine changes, genetics, environment, immunity and other factors, resulting in a bag inside the patient’s mouth, which can seriously affect the patient’s eating and speaking. 3. Herpes: this disease is mainly caused by human herpes virus infection, spread through direct contact, indirect contact, resulting in a bag inside the patient’s mouth, common symptoms include fever, pain, local lymph node swelling. 4. boils: due to the staphylococcus aureus and other causes of individual hair follicles and the surrounding tissues are invaded, so that the patient’s mouth inside the growth of a bag, but also local redness, swelling, pain and other symptoms. It is recommended that patients go to the hospital in time, under the diagnosis of the doctor, according to the patient’s condition, targeted treatment, so as not to cause adverse effects on the body.