It could be IBS, but he might just be ultra sensitive. Ripley had very similar symptoms when he was younger. He had hives all over, and his coat just wasn't very nice. His stools alternated between pudding consistancy and explosive diarrhea, he couldn't keep weight on, he was very gassy some nights, etc. Our vet also wanted to put him on Metronidazole as he was at as much of a loss as we were, but he didn't have anything wrong with him other than severe food intolerances. We did a couple rounds of the metronidazole just incase, which just made things worse as then his gut flora was all messed up, so we had to give him digestive enzymes or (non-dairy) acidophilus.
It was a lot of trial and error, but we finally found a food that agrees with him and he looks fantastic. Coat is beautiful, skin is healthy, stools are perfect, weight is good, etc. I found, oddly enough, that both of my sensitive dogs did the worst on limited ingredient foods like CN for some reason. I have no idea why, though.
Sorry, not really all that helpful! But I hope you're able to get to the bottom of it. Food issues are no fun at all.
It was a lot of trial and error, but we finally found a food that agrees with him and he looks fantastic. Coat is beautiful, skin is healthy, stools are perfect, weight is good, etc. I found, oddly enough, that both of my sensitive dogs did the worst on limited ingredient foods like CN for some reason. I have no idea why, though.
Sorry, not really all that helpful! But I hope you're able to get to the bottom of it. Food issues are no fun at all.