The child’s mouth is always long ulcers are considered to be due to bad habits, lack of trace elements, local infections and other reasons. 1. bad habits: if the child has the bad habit of picking his mouth, biting his lips or biting the pen, so that the local long time stimulation, causing the local mucous membrane abnormalities, which can lead to the child’s mouth is always long ulcer symptoms. 2. Lack of trace elements: if the child has picky eating, partiality and other bad dietary habits, so that the body’s resistance to decline as well as the lack of trace elements needed in the body, will cause skin tissue abnormalities, which can lead to the symptoms of the child’s mouth is always long ulcers. 3. Localized infection: when the child’s mouth is locally infected by bacteria or germs, causing damage to the skin and mucous membranes, if the affected area is often stimulated, it can lead to the phenomenon of ulcers in the mouth. Children always have ulcers in the mouth may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.