If your dog brings up undigested food immediately after eating, there are high chances that you may be dealing with regurgitation rather than vomiting. So, it is important to understand the difference between the two before you take any action. When a dog is regurgitating, the process of bringing up the food tends to be more passive. In most cases, your dog will lower his head and cough out the food passively. The food comes out with ease, without significant muscle contraction.