I have a four-year-old Boxer who has a very
strange thing happening. He is throwing up a foamy
white discharge. He first threw up yellow bile. I also
accidentally bought him the wrong food that he has
been eating for a couple of days. I just noticed
last night that I bought a prescription food
called Skin Support. He is supposed to be on Potato
and Venison Prescription food. Do you think this
might of caused this strange reaction? I am
worried about him.

Sugar Ray
Miami, FL

There is a good chance that your dog’s accidental diet change is playing a role in the problem you describe. In fact, any time a pet’s diet is changed suddenly, gastrointestinal upset may occur.

This can happen even if both diets are high quality, and almost all prescription diets fit that description. However, if your dog’s gastrointestinal system was accustomed to the original diet for a long period of time, the sudden change could have triggered inflammation (which is how veterinarians say irritation). Inflammation can lead to vomiting or diarrhea. The problem typically resolves shortly after switching back to the old diet, but in severe cases it may be necessary to feed a special, highly digestible diet until calm things down.

As a general rule, when you want to change your pet’s diet, the best way to prevent gastrointestinal problems is to make the switch gradually over the course of several days. Of course, that advice doesn’t apply in your case, since you didn’t mean to change your dog’s food.

In this case, there is also a chance that something else may be causing your dog to vomit. If he does not stop vomiting within a few days of changing back to the Venison and Potato diet, or if he is lethargic, not eating, having diarrhea, or acting sick, you should take him to the vet.

Also, remember that his original diet, the Venison and Potato formula, is a prescription diet. If he was eating that diet due to a medical condition, you should check with your vet to make sure that the accidental food switch won’t interfere with his treatment.

Finally, you mentioned that your dog was originally vomiting yellow bile, but is now bringing up white foam. Be aware that white foam can originate in the gastrointestinal system, but also can come from the lungs. If there is any chance that your dog is coughing up the foam, rather than vomiting it, he should go to the vet immediately to have his heart and lungs assessed.