11 months baby mouth odor may be due to improper hygiene cleaning, or may be due to gingivitis, chronic tonsillitis and other diseases. 1. Improper hygiene: If the mouth is not properly cleaned, it can lead to the fermentation of food residues left between the teeth, resulting in a foul odor. If the baby does not have other symptoms of discomfort, it is a normal phenomenon, no need to worry. 2. Gingivitis: Gingivitis may be caused by plaque, food impaction, mouth breathing and other factors. The child will have bad breath, red and swollen gums and other symptoms. 3. Chronic tonsillitis: the mechanism of chronic tonsillitis is not yet clear, it may be caused by local bacteria, poor drainage of tonsil crypts, low immunity and other factors. When the tonsil crypt memory has tofu dregs-like corruption, can be accompanied by anaerobic bacteria infection, can appear bad breath. 11 months baby bad breath, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.