Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today.
Now I would note that we can see oral odor for a range of reasons. Common causes are dental disease, oral sores, nasal infections but also GI changes. Often with bacterial, viral, protozoal or even foreign body or stomach ulcer induced GI upset we will smell a change in breath (sometimes quite pungent and unpleasant). So, that is a concern for Gordon especially if he is vomiting and has loose stools.
Now if he has pale gums, belly pain, black stools or you think he ate something harmful, we'd want him seen urgently. Else we can try some home supportive care to try to settle his stomach and with it his breath. To start, if he hasn’t just vomited (since otherwise we’d need to rest his stomach for a few hours first), then you can consider treating him an OTC pet safe antacid [ie Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac)]. Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned. Though if he cannot keep it down due to nausea, that is usually a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.
Afterwards, you can consider starting an easily digestible diet like cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until signs are settled, and then weaning slowly back to your normal diet.
Furthermore, as long as there is no blood in those stools, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure for infectious issues; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p)). This is available OTC at most pharmacies. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (all OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. And if the odor is quite strong, OTC activated charcoal could also be used to bind that (but again usually treating the GI issue will settle the oral smell).
Finally, as dehydration is a risk here, we need to keep an eye on his hydration. To check that he isn't dehydrated, there are a few things you can test. Further to checking for gum moisture, do make sure he doesn’t have sunken eyes and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have him seen before this becomes an additional issue (especially as it is often dehydration that makes them feel unwell).
Overall, Gordon's signs do raise some concerns here. Therefore, we’d want to start supportive care to settle his stomach. If he cannot keep that or water down at any point, appears dehydrated already, or doesn’t respond to the above within 12-24 hours; then we'd want to get his vet involved. They can assess his hydration, rule out fever, make sure there is nothing in his stomach that shouldn't be there or any sinister viruses present. Depending on their findings, his vet can treat him with injectable anti-vomiting medication +/- antibiotics to settle his stomach, and get him back feeling like himself.
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