If you're not worried about his skin, what is it you're asking for advice on?
Having said that, although stress can trigger problems, it's important to still manage them rather than using that as a cause for dismissal. None of my rats have ever had dry itchy skin in old age. What makes you say that you know he doesn't have mites? If his symptoms are ones that would make you think mites in a younger rat then I would treat him - it's probably the first thing a vet would recommend too. For one thing, rats get mite flare-ups if their immune system dips for any reason, and one of the key causes of that can be stress
Unrelated to your old boy, but is your 8 week old getting company of another kitten?
I know he dosent have mites etc SO I'm assuming his old age is partly to do with his dry itchy skin. He also gets vitamin supplements in his drinking water & Salmon/cod liver oil in his food. Could Younger cage mates be causing him stress. He lives with an older boy of 2, two 12mth boys & an 8 week old. All the Boys get on great, no fighting Although one of the 12mth boys is bouncy & cheeky and My old Boy has pinned him & pulled his fur out in the past When youngster dared to pinch his treat. I know he's getting on & I'm a Fussy Ratty mum BUT any help, Advice would be welcome 
Just letting ' the Boys ' know ' He's still the Boss 
