Aahh….aren’t senior dogs wonderful! I’m not an expert, of course, but it seems to me that there is some kind of intolerance going on. If she were my dog I would keep giving her probiotics/enzymes and find a food without chicken and grains. Tractor Supply has a nice grain free kibble that contains Whitefish and Potato (4Health, their private label brand) and it’s pretty much a limited diet. I don’t know how big she is or if kibble size is an issue but the kibble size of 4Health is not tiny. They also have a limited ingredient can food there (I believe Turkey & Sweet Potato) for .99 a can. There are some other hypoallergenic diets that are listed on this site that might be good options, too. Go to “best dog food” and then look for hypoallergenic. I’m sure others will post here soon. 🙂
