Twelve year olds with bad breath need to pay attention to oral hygiene, you can rinse your mouth and brush your teeth more often. If it is triggered by different degrees of digestive diseases, it needs to be treated. 1. Simple oral hygiene triggered by bad breath can be improved by strengthening the way of oral cleaning such as gargling and brushing teeth. (1) Mouthwash can be used to gargle after each meal, 10~15 ml at a time, but the choice of mouthwash needs to be careful, some medicated rinses are only used for periodontal scaling and post-surgery, and are not used as a daily oral care product, and can not be used for long-term gargling. When the disease is cured should stop using, so as not to cause the normal flora in the oral cavity disorders and drug resistance. (2) Brushing: You can choose the toothpaste that inhibits plaque and reduces inflammation of the gums. This kind of toothpaste can inhibit plaque or reduce the inflammation of the gums such as redness, swelling and bleeding through the action of chemical composition. 2. If bad breath is not caused by oral hygiene, then we need to consider the possibility of digestive diseases. (1) constipation: children’s constipation can be divided into functional constipation and constipation caused by congenital intestinal malformations, at this time we need to clarify the cause of the disease, if functional constipation can be adjusted to the dietary pattern, pay attention to more water consumption of food with more fiber, if the intestinal malformations triggered by the need for timely admission to the hospital, surgical treatment. (2) gastrointestinal tract inflammation: this time and use can be triggered by viral and bacterial infections, resulting in gastrointestinal tract inflammation, this time we need to consult a doctor in a timely manner for symptomatic treatment, to avoid aggravation of inflammation affecting health.