Yes, it can be harmful to your dog to eat their own vomit. However, they also regurgitate their food and then eat it.
Dogs eat their own vomit because they still see it as food. Their superior smell receptors allow them to recognize that there are still nutritious food particles in there and that seems tasty to them.
Dogs sometimes eat their own vomit because to them, it still smells tasty. But, just because it’s tasty, doesn’t always mean that they should eat it.
Dogs eating their vomit is very normal. When dogs are still puppies, they drink from their mother. By three weeks old, as they start weaning from natural milk to food solids, their moms will chew food and regurgitate it.
Eating regurgitated food won’t pose any medical problems. Eating vomit, on the other hand, is not healthy. The food is ejected from their stomach, which means it is mixed with high levels of stomach acid.