The white or pale yellow foamy phlegm a dog vomits is called bile. Dogs that vomit bile, usually in the mornings or after a very long period of sleep, suffer from bilious vomiting syndrome, which is also called reflux gastritis. Dogs vomit the foam and then seem fine. This is an alarming, but treatable condition and should be monitored if it gets worse or does not respond to home remedies.
The main cause of bilious vomiting syndrome is that the dog's stomach is full of bile. Usually, bile is farther down in the digestive system and does not creep up to the stomach. But, if the dog's stomach lining is easily irritated or especially sensitive, even a small amount of bile on an otherwise empty stomach is enough to make it vomit. Bile can build up in a dog's stomach when it sleeps.
Dogs that have suffered from serious gastrointestinal illnesses, like pancreatitis, irritable bowel disease or giardia infection, will be more prone to developing a sensitive stomach, according to Holly Nash, DVM. Another problem is chronic gastritis, which can be caused by many types of illnesses. Other symptoms of chronic gastritis not usually seen in bilious vomiting syndrome are loss of appetite, flinching when the abdomen is touched and weight loss.
Dogs with bilious vomiting syndrome tend to eat grass and vomit soon after awakening and then act normally throughout the day. This only happens once or twice a week or less. Dogs that vomit white or yellow bile every day and have watery diarrhoea may have be suffering from internal parasites, such as giardiasis, according to "Dog Owner's Home Veterinary Handbook." These dogs need to see a vet as soon as possible.
For dogs that are vomiting bile and show no other symptoms, try a home remedy. Feed a light snack late at night or at least seven hours before the dog has to wake up in the morning. Start feeding the dog a small breakfast if the dog does not already eat more than one meal a day. The food will help absorb the bile. This helps keep the stomach lining from becoming irritated and making the dog nauseated.
In order to determine the cause of chronic vomiting of bile, a veterinarian will need to examine the dog and test the most recent stool sample possible. The dog may need to go under anaesthesia to have an endoscopic examination of the stomach. Another test is a liquid barium test, where the dog swallows liquid barium before being X-rayed. This liquid makes the X-rays clearer and helps to rule out internal injury, a tumour or the presence of a small object the dog may have swallowed.