White foam is mainly caused by the loss of consciousness and the loss of swallowing function, so that the saliva in the mouth is accidentally sucked into the trachea. But the patient’s breathing is normal, so the saliva will mix with the exhaled gas and spit out in the mouth, thus forming a bubble-like white foam. Most of the diseases that cause sudden loss of consciousness are mainly brain diseases, such as transient lack of blood supply to the brain, transient cerebral ischemia due to cervical spondylosis, or sudden cerebrovascular accidents such as cerebral hemorrhage and cerebral infarction. Transient syncope can also occur in acute heart diseases, such as acute myocardial infarction, angina pectoris, etc.