The majority of babies with mouth foam in 40 days are normal physiological reasons, parents do not need to worry excessively, but a few may be caused by pathological reasons, such as respiratory tract infection, such as other abnormal performance, you need to promptly seek medical advice to clarify the cause and give the appropriate treatment. 1, physiological reasons: most babies may appear after drinking milk foam phenomenon, this is because the pacifier stimulation when drinking milk This is because the pacifier stimulates the salivary glands of the baby’s mouth when drinking milk, causing an increase in saliva secretion. At this time, the baby’s oral function is not yet developed, the mouth is shallow, and the swallowing ability is not yet developed, which leads to the phenomenon of spitting up foam, this is a normal physiological phenomenon, no special intervention and treatment; 2, pathological reasons: usually caused by respiratory tract infection. If the baby has a lung infection, it will lead to a faster respiratory rate, and at this time the baby’s cough reflex is not yet developed, which can be manifested as breathing difficulties, foaming at the mouth, poor mental state and other symptoms, you need to promptly take the baby to the hospital for further examination and treatment after clarifying the cause. According to the results of the sputum culture drug sensitivity test, active anti-inflammatory and anti-infection treatment can be carried out according to medical advice. If it is caused by bacterial infection, antibiotics can be used to control the infection. If it is caused by viral infection, the main treatment is symptomatic treatment, such as the use of phlegm and cough medicine, and also the use of nebulized inhalation drugs to dilute the sputum, if it is caused by mycoplasma infection, the use of anti-mycoplasma drugs for treatment.