The child’s mouth stinks of bad breath, may not pay attention to personal hygiene, indigestion, oral inflammatory diseases and other factors. 1. Do not pay attention to personal hygiene: usually children do not brush their teeth properly, do not rinse their mouths in time after meals, a lot of food residues remain in the mouth. The fermentation of food debris will produce a foul odor, resulting in bad breath and bad breath. 2. Indigestion: The usual unhealthy eating habits will increase the burden of digestion and absorption in the gastrointestinal tract. The slowing down of the peristalsis of the gastrointestinal tract leads to the accumulation of food in the gastrointestinal tract for too long, which may also produce unpleasant gases, which in turn leads to bad breath. 3. Oral inflammatory diseases: children suffering from gingivitis, periodontitis and other oral inflammatory diseases, pathogenic microorganisms in the oral cavity will induce a large number of growth and reproduction of local inflammatory response, may also lead to the child’s bad breath halitosis. There are other clinical causes of bad breath in children. Parents are advised to take their children to the pediatrics or stomatology department of the hospital as soon as possible to identify the specific causes of bad breath.