One of the most common reasons that dogs vomit white foam is because of an upset stomach. According to VetInfo, this often occurs if the dog drinks water too quickly, eats grass or ingests something inedible that upsets its stomach.
Another reason dogs vomit white foam is because of bilious vomiting syndrome, which usually occurs right after dogs wake up. Veterinarians believe that the syndrome is caused by too much stomach acid or other secretions that collect in the stomach and cause irritation. This occurs most frequently in dogs that already have digestive problems.
White foam is also a sign of bloating, which is a swelling of the stomach that causes it to rotate. This rotation traps the stomach’s contents and obstructs the veins around the stomach. It is usually accompanied by other symptoms, such as pacing, anxiety, restlessness and a hard abdomen. If it is not treated, it leads to death.
Yet another reason dogs vomit white foam is because of kennel cough, which is an upper respiratory infection that is contracted from other dogs. Dogs suffering from kennel cough have a dry cough and experience flu-like symptoms, such as nasal discharge, sneezing and fever.
Finally, vomiting white foam is a sign of rabies as well. The foaming around the mouth is caused by nerve damage around the mouth and throat, which prevents the dog from swallowing. However, dogs do not begin exhibiting this symptom until the later stages of the disease.