
I would suggest the raw feeding too. It is well known that a natural raw diet can help remedy various allergies, smelly dogs, teeth and gum problems, over excited dogs and temperaments too.
As mentioned, you will be in total control of what is in his diet, and know exactly what you have given him.
Variety is essential, and include raw bones and various offal types too.
Do some research into feeding a raw diet, it is very easy and NOT a problem as some like to make it, change over can be quiet quick.
Have a look at "Natures Menu" frozen meats and complete meals, their Country Hunter products are very good. (all clean and no blood)
Prescription diets are frequently loaded with cheap fillers many of which can cause allergies themselves. And many of the products that are suggested by our vets, you can be sure they are selling themselves too !
Some little books that are easy reading and easy to understand may help you. Look on Amazon for "Honeys Natural Feeding for Dogs" and "Works Wonders" by Tom Lonsdale. Used books are like new, sometimes from 1p each