Question for Dog Owners...

The cats could have mites and they have spread to the dog. They don't always spread fast. My ex's cat had them, and they spread, but it wasn't like a wildfire. It took a bit of time before we realized. When patches of fur are starting to come off, it looks like whatever it is, is starting to become troublesome, and the last thing you would want is mites spreading through your house too (if that is what it is). At this point, it's been about a month since you started the thread, and it looks like it got worse. I think a vet trip is a good decision.
 
That does look miserable - I didn't think hind quarters was a typical spot for doggy eczema.You have vet advice above - can't do better. Took my dog to a doggy derm. once - $500 without any testing. Some pretty decent advice above except topical Benadryl (sorry) which causes contact dermatitis, esp.in more sensitive breeds, and topical steroids - if it is an infection it can become a lot worse by using topical steroids. Is the problem year round or seasonal? Is he on good, reliable flea treatment? Diet questions are also legit.

I do agree it does warrant a vet at least to do simple scraping, rule out fungus or ectoparasite issues, intradermal skin testing, etc. YI'm sure its owner would hate to miss some serious/rare like CTCL. My dog's eczema treatment was basically with a round of oral antibiotics, a short course oral steroids, and chlortrimeton (OTC chlortrimeton is safe and dosed by body weight). Supplements including Tumeric, salmon oil/omegas, flaxseed, coconut oil & zinc can help and are pretty safe. Sulfodene is reasonable and pretty much a do-no-harm too. The pro's seem to be fond of Apoquel or Cytopoint for eczema; they may be recommended and are great treatments..but are pretty pricey.
 
Again, I'm not a vet, I just helped a few maintain their status of living with my Cocker Spaniel.

Well I can tell you this shit stumped several vets regarding my Cocker. I'd also look into breed specific problems. Cockers are known for skin issues but also for a bunch of other problems. So bear in mind this might not be just one issue (which was my case and why it was so damn hard to fix).

The vet will wanna do an allergy test at some point if it's not something obvious.

That's why I bring up the prednisone as a last resort. It's not something you wanna have to give the dog daily forever BUT it was the ONLY thing that gave that poor Cocker respite for the last five years of his life. It was a TINY dose that did it, but still. Just something to bring up with the vet if all else fails.

Before he was on it for life though he'd get a round of it and it'd clear him up for a while. That may be your case, it's like a silver bullet for a lot of problems it can just be hard on the body. ANY steroid like that can be bad though and there's a reason why prednisone can be especially bad, so for sure talk to a vet first.

I CAN tell you this: if you don't stop the chewing, even if it resolves, the problem won't. You're gonna NEED an e-collar (elizabethan collar, "the cone" or whatever you wanna call it). It becomes a habit for 'em and it sounds like it's been going on long enough for that to be an issue. My setter will get an itchy ass from time to time, will just quietly and calmly suck on his asshole for hours like it's the tastiest lollipop in the world if you let him. Problem goes away and then I have to break him of the habit for a few days again. Mine doesn't mind the collar at all, now nail trimming is different...

There are a few sprays that help with chewing but I forget which ones work, it's been a while. It had something in it though, wasn't homepathic or whatever. You do wanna be careful with topicals, talk to a vet, because they'll just lick it off. You don't want them licking something they shouldn't.

Poor pup. BTDT, it sucks.