Symptoms for dog food allergies are the same as symptoms for many other forms of allergy, so hopefully some light will be shed here for you - meaning you do not have to jump through a whole lot of hoops unnecessarily!
There is a very long and tedious method of how to identify what a dog may be allergic to in dog food but consider this - it may not be the dog food at all but plants, household chemicals, garden treatments or even some human food "treats".
Paw licking, general licking in various body areas, scratching, could be the result of any one of these other possible causes - so please do not only think of food as the culprit.
Your vet and other options are discussed below.
Your vet's probable method.
To try and identify a dog food allergy vets will usually commence a twelve week process called a "food trial" or "elimination diet" - which when conducted means the dog has to be closely monitored so as nothing other than the "prescribed novel food source of protein and carbohydrates" is consumed by the dog.
NO dog treats or rawhide, pigs' ear, medications that are flavored to be "tasty", no bones, no licking the cat dish, no raiding garbage bags or bins, in fact absolutely nothing other than the "novel" food source must be consumed by the dog - except of course water.
Your dog's movements also need to be restricted to an area where no such "temptations" could arise, or possible food droppings be found, so no roaming is allowed either.
This "novel" food would consist of food the dog has never consumed before in its' regular diet.
Then of course if the problem is not solved with food plan "A" you will need to go to food plan "B" for another twelve weeks, and so on and so on - over and over again!
All in all it is not an easy task but if all else fails then a food trial or elimination diet may be your only option!
Here's some "easy to do options" that may find a simple solution, or a different cause of the allergy.
Your Dog Food
Dog food allergies have a few "prime suspects" and by just dropping a dog food that contains certain ingredients will result in a positive outcome.
First step would be to look at the ingredients listing of the food you are buying.
Have a look at my dog food ingredients section. If your food contains one or more of the listed "unwanted" ingredients, plus maybe splitting or grouping, then I would certainly consider a change of dog food.
Your solution could be that easy!
Grains in dog food always come up as a "suspect" because they are not seen as part of the hereditary diet, so visit my grain free dog food section for more information on that subject.
Also visit my hypoallergenic dog food section in your fight against dog food allergies.
Do you know it could also be as simple as changing to a BARF diet because you will be in control of what is going in to the food? My page on the BARF Diet has more information plus links to where to get recipes and further guidance.
Outside of the dog food arena there are a few other possibilities and the one that comes to mind first is plants. These could be within your garden or outside when you take your dog for walks.
In my plants and your dog page I have a couple of links to some excellent resources that will give you plenty of help in what not to have your dog come in contact with.
One amongst those links is allergy free gardening (new window opens to website) which may be all you need to identify a possible problem causing an allergic reaction.
My plants and your dog page also lets you know the household items that can cause problems.
Food bad for dogs should also be viewed because if your dog is being given a unsuitable "treat" that may well be cause of a negative reaction by your dog.
Last, but by no means least, in your search I would also suggest a visit to dog food additives as part of your elimination process.
As I said at the beginning detecting dog food allergies is no easy task but in my mind there is nothing more concerning than seeing a dog constantly licking or biting itself - especially when you are certain your dog is flea free!
There you have it - plenty to do and try in dog food allergies before heading off into the food trial and food elimination twelve week program/s!
Mind you if money is not a problem you could also get your vet to run allergy testing samples from your dog but it will not be conclusive if it is not as wide ranging as to cover all of our possibilities mentioned above.