Depending on variety of reasons which range from the type of dog breed, diet, and feeding habits, many dogs go through the unpleasant experience of chronic bile vomiting. This is not fun for the dog and may lead to other health issues and is certainly not suitable to the rest of us who don't have yellow carpet.
But what is that yellow stuff?
That [foamy] yellow stuff that you keep cleaning up is bile, which is the digestive fluid that helps break down the food once it passes the stomach and enters the small intestine. Normally this, like in humans, another ingenious process pulled off by mother nature that we take for granted...until you notice yellow foam on your kitchen floor.
The reason why dogs can experience a chronic issue with puking this yellow foamy bile has to do with their stomach actually. The bile is created in the liver and stored in the gallbladder...normally when food enters through the stomach and passes to the small intestine that bile is released into the small intestine to help break down the food. If their is no food in the stomach to pass to the small intestine for an extended period of time, what happens is the bile can creep into the stomach causing an uncomfortable, nauseous feeling for the dog...a few minutes later you may see your poor dog hunched over in this position.
So what do I do?
Fortunately, for the most part this is something that's treatable...obviously if the vomiting gets more frequent, violent, and/or it's not yellow, then certainly contact your vet (more below). But the reason has to do with your dog not having enough food in his stomach...hence why you probably notice the puking in the morning after 8 hours of sleep or at night after he's waited through the day for a meal.
What you can do is, not necessarily feed him more food, but feed him smaller meals more often especially later at night before bed. If that doesn't work, vets may recommend adding in food that's low in fat and/or fiber content. They may even recommend trying canned or liquified meals in addition to see how their stomach reacts to that. Either way the name of the game is making sure your pup's stomach is not empty for a long period of time...I mean after all can you imagine being that parched or hungry you didn't have anything in your stomach for so long you actually puked!
If your pup experiences any of these signs/symptoms below you should contact your vet: