When a dog vomits yellow foam, the dog's stomach is likely empty, and it is partly vomiting the yellow bile produced by the liver that helps in digestion, explains Vetstreet. The fluid is stored in the gall bladder and released as needed into the small intestine right past the opening to the stomach. Because there can be various factors that cause a dog to vomit on an empty stomach, you should see a vet if this occurs.
To address this condition if the dog is otherwise healthy, a vet often recommends to break up the dog's feeding times into various periods during the day, according to Vetstreet. This does not necessarily mean the dog needs more food, but give its daily portion in several feedings. If, however, there are other substances in the vomit, and they are identifiable, such as grass, prevent the dog from ingesting these substances.
If the dog has other symptoms aside from the foamy, yellow vomit, such as lethargy, diarrhea or a yellowish hue to the skin, eyes or tongue, the veterinarian can conduct further analysis to rule out underlying conditions, adds Vetstreet. Factors such as sudden diet changes, stress or side effects from a medication may be causing these symptoms, but they can also be caused by more serious diseases or parasites.