Infant sleep spitting bubbles may be caused by normal physiologic factors, such as salivary gland development. There may also be pathologic factors such as respiratory or digestive diseases, this is not normal. 1. Physiological factors: after the development of infant salivary glands, the mouth will generally have a small amount of saliva, at this time, if the baby’s swallowing function is not fully developed, can lead to the baby will not swallow saliva, when the exhalation, the saliva is not swallowed will appear in the mouth and lips between the saliva wrapped in bubbles, i.e., spit bubbles. This is a normal physiological response. 2. Pathological factors: such as respiratory or gastrointestinal diseases, may lead to the baby’s poor breathing, nasal congestion and ventilation, this time may also be in the exhalation of spit bubble phenomenon, while the bubble is generally more viscous, small, this is not normal. Babies sleep spit bubbles may have other reasons, excluding physiological factors, should be timely medical examination and treatment.