
Hi Noel,
The best way, apart from having allergy testing done by a lab, to ascertain whether a food based allergy or intolerance is affecting a dog's tummy or skin is to put the dog on an "exclusion trial diet". This means picking a food which has a minimum of ingredients and is ideally designed for sensitive digestive systems - these also tend to be high in Omega 3 & 6 oils which are good for the skin :)
The best non-prescriptive ones I know of are Wafcol Salmon & Potato and James Burns - both of these are dry completes - or if you're leaning towards a moist complete then you could try Nature Diet Sensitive Gold.
As Digger points out, gluten is a known allergen for many dogs and is present in several forms. The above are free of
all gluten sources :)
IMO, the better of them from an exclusion trial point of view would be the Wafcol Salmon & Potato as these ingredients are rarely in other commercial foods - unlike rice which is widely used.
The main key to an exclusion diet's success is that absolutely
no other foods, treats or titbits are given - this includes such things as pigs ears, rawhide chews, even drinking the leftovers from your cup of tea ;)
You have to stick with it for at least 6 weeks (providing there are no adverse reactions) to give the intolerant ingredients time to be fully removed from the system and to give the new food time to work towards improving the original condition.
HTH, best wishes, Teri :)