I do agree with our resident veterinarian, that the immune system can't be boosted, it just is. However, there is such a thing as a dysregulated immune system, which means that it is less effective in dealing with everyday pathogens which a fully-functioning, healthy immune system has no problem with dealing with "all in a day's work".
Unfortunately, the current orthodox medical way of dealing with a dysregulated immune system is to suppress it with drugs like Apoquel
which will exact a toll on your dog at some point, a very eminent physician I know told me once that all medicine is poison.You really want to try and address the underlying cause of the immune dysregulation which immune suppressants clearly do not do.
What I would do if I had a dog with the issues yours have is definitely feed raw. However, it is likely not to be enough because once a dog is dealing with immune dysregulation it is really difficult to reverse. If I could find a competent homeopathic vet I would consult them (or do a phone consult). I would definitely give him the supplement 4life Transfer Factor
. But most importantly, I
would stop the pharmaceutical assault on his immune system by stopping all vaccinations from this point on, you can get a "waiver" if you need it for boarding, training, groomers etc. Antibiotics really don't help immune function either, because they mess up the gut, and as 80% of the immune system resides in the gut, you really don't want to decimate the microbiome with antibiotics, so I would be giving my dog probiotics to help his microbiome recover, again, a very difficult thing to achieve once it is out of whack. You could try putting Manuka honey
on the affected areas of his skin. Vitamin C* is also very effective in the healing of skin infections and has been shown in research to cure MRSA infections. You can give it internally, on add it to a carrier cream and apply directly to the skin. I would also try coconut oil both externally and internally.
Good luck to you in healing your dog.
* Sodium ascorbate is the form to use or liposomal vitamin C which is even better because it is a highly bioavailable form.