What causes yellow vomit or white foamy vomit in dogs, and how do I respond?

Quick answer

Yellow vomit is bile reflux, usually 'bilious vomiting' that happens when the gap between meals is too long. Shortening meal intervals or offering a small snack before bed usually resolves it. White foamy vomit is stomach acid or saliva mixed with air, commonly from mild indigestion or drinking water too fast. That said, if your dog seems lethargic afterward, refuses food, or vomits more than 3 times a day, it could signal a foreign object or pancreatitis — see a vet.