[MaisieAndGem]

Is he an outdoor or indoor dog now? Are there any plants in particular in your yard that he reacts to?

What shampoo do you use?

What advice has your vet given you on all this? Is he losing weight?

Is there any particular reason you feed him fish rather than red meat or chicken?

 

[MaisieAndGem]

Poor boy! I know it may be hard, but switching his food so often could contribute to the problem. If the Royal Canin was helping, then go back to that with a mix of whatever dog-safe vegetables and meat he is able to eat. As long as he is not losing weight, just let him pick at it. Leave the food down all day so he can eat when he feels like it.

Hills Prescription diet has a decent range of dry and wet foods for health issues like these as well, if you haven't tried it already. You sound like you are doing the very best you can for him, but don't overcomplicate things. As long as he isn't dropping weight, it may just be a waiting game to get him to used to a new food.