I'm sorry Kenzo has been poorly and understand you will be worried for him.
As dogs get older, it is inevitable they will start to develop some age-related issues. As Kenzo is a Boxer, he does likely have some joint disease and arthritis which could be a factor in his mobility problems and slowing down.
Dogs will lick their joints when they are in pain and the saliva can cause the fur to change colour.
However, we would not expect the other signs and these are probably telling us there is something more serious going on.
His signs of frequent vomiting, weight loss, excess thirst, a reduced appetite and panting could have several causes including:
- Liver disease
- Kidney failure
- A protein losing disorder
- A gut obstruction
- Heart failure
It is important he sees a vet who can check him over and will likely run some tests such as a blood test and abdominal scan, so we can get to the bottom of this.
His treatment options will depend on what is going on.
At home, offer small and frequent meals of something easily digestible like chicken and rice alongside plenty of water.