Uncontrolled Itching

[Whisky]

My Campbell's hamster Koosh is about 21 months old now (getting up there, I know) and has severe itching. He's seen two exotics vets and been examined multiple times.

Things we've tried: Revolution (for mites, 3 times), TMS (in case of bacterial infection), Baytril (same reason, and for an abscess he had at the same time), Metacam (for inflammation and pain relief), and diphenhydramine (an antihistamine, which I think made his eyes dry and sore).

His main vet (who is knowledgeable about hams) is as frustrated as I am because, as she says, it simply doesn't present as anything. It doesn't look like any specific condition. He has raw scabby areas on his face and abdomen, but no sign of infection or parasites. All the marks are dry and self-inflicted.

The only thing that seems to help is the Metacam, and it doesn't stop his scratching at all, just provides some pain relief, I think. He was pretty quiet and not himself a couple weeks ago, so we put him back on the Metacam and he bounced back quickly. He just won't stop scratching!

His scent gland may be infected, too - it's been swollen and red, and I removed a hard plug from it yesterday. He's still scratching it.

I'm going to call his vet tomorrow to update her, but I think she and I are out of ideas. I know Koosh is old, but I really want him to be comfortable while he's here. So I'm just wondering anyone else here might know of a solution, or an explanation, or might have experienced this with their own hams. Any replies would be welcome. Thanks.