Causes of bad breath in one year old babies may include untimely cleaning of the mouth, digestive disorders such as gastritis, oral diseases and so on. 1. Failure to clean the mouth regularly: If you don’t brush your teeth on time every day, you may have bad breath. After breastfeeding or before going to bed at night, you can use wet cotton gauze to gently wipe the baby’s teeth, and pay attention to feed the baby more water to avoid causing bad breath. 2. Digestive system diseases: such as gastritis, gastroesophageal reflux disease, etc., there may also be lactose intolerance, food allergies, etc., resulting in increased gastrointestinal tract gas, thus causing bad breath. It is recommended to go to the hospital in time for examination and treatment according to the cause. 3. Oral diseases: such as mouth ulcers, herpes stomatitis, etc., can be treated according to medical advice. Babies under one year old within the need to drink more water, the diet should be rice soup, noodle soup and other easily digestible food, do not eat sweets, snacks before bedtime.