The first object your vet will have is to reduce the discomfort for your pet, and there are a number of different foods created as tools to help with this in that unusual protein sources are used as a single ingredient food that may eliminate the itching, sneezing, scratching type of stress that both you and your pet are under while the allergy or intolerance continues.
Here in Canada, according to the available foods in stores and veterinary offices, it appears that the standard protocol taught in veterinary schools uses what is called an "F&P" diet, meaning fish and potato. Other countries seem to lean toward other unusual protein sources such as rabbit, which I would prefer to see, myself, as fish is not a great source of B vitamins for pets and usually there is a general rule to use no more than 30% fish in a pet diet. Humans can make this up with leafy green vegetables added to their plate, but this is not expected to be found in commercial pet foods, and carnivores are not known for their plate of salad beside their kill in the wild that isn't normally fish for cats and dogs.
Sometimes there is sweet potato on the label of foods designed for elimination feeding, but there is little difference between that and regular potato when it comes to nutritional content for pets. The weakness with this particular combination in my mind is that some pets need to restrict postassium levels, and potato is high in postassium. As I have stated before, though, there is no perfect pet food, and the priority here has to be elimintating the source of irritation.
If the first single protein choice is found to eliminate the irritation which took you and your pet to seek veterinary advice, this is the first step in recovery, and you are lucky. Usually, if it doesn't work, another single protein source is picked, such as lamb, beef, and even grain proteins are resorted to. Most of the time the use of rice, or the better protein source of corn gluten meal will work fine in the short term, but there is the odd time that corn has been found to be a cause as well.
Other possible problems with food allergies may be the additives other than proteins such as guar gum, (diarrhea), dairy, (bad stomach pains and sometimes diarrhea), and so on. This means that for some pet owners there may be a long tedious process that will require a lot of patience on your part as your animal remains in discomfort for a longer period of time.
The allergy may have to do with how the source of protein was grown, or processed. This may involve growth hormones, as used to be common in North America when raising poultry, (now banned here), or it could be in a chemical used in the processing of vegetable matter such as the use of sulphites.
This is just the beginning of the journey to resolution of your pet's food issues. There are a number of other items on the ingredient list that may be found to be the irritant for a pet's problems from dermatitis, to asthma, to seizures, IBS and other indications of toxic reaction. Some good general sources of information can be found at the following sites:
Drs Foster & Smith: Peteducation.com has an article called
"Food Allergies and Food Intolerance" with the guidelines for feeding an elimination diet about half way down the page.
Laboklin Aktuell has a pdf file you can download with a slightly different perspective on food irritants at a site labelled,
"Adverse food reactions in dogs and cats"
There is another point of view at
"Food Allergy In Cats: Symptoms, Treatments And Diagnosis" but that site doesn't go into as much detail regarding how to handle an elimination diet.
There are more sites online that refer to food intolerances, but one problem I am finding with even the latest site listed last above, is that alternate triggers are not being addressed. Some of the triggers can involve
sulphites or
MSG that can be a
by-product of protein production.
While coloring and flavoring agents can be among the worst triggers, (look at the struggle around pinpointing ADHD triggers), along with being neurotoxins or exitotoxins, I found it harder to find online information on these for pet foods. However, eHealthMD offers a good
overview of a variety of triggers as mentioned above from a human perspective, and colorings are listed at Allergicchild.com under the page
"Food Dye Intolerance and Allergy". The
yellows and reds are possible triggers for your pet. Another chemical to look for in ingredients you see listed fits into this "dye" category as tannins are also dyes. Some sources are listed if you click
here and a site that may help you understand why the body can't accept tannins is
here.
A book that is available, which might help identify reasons for your pet to have IBS, for instance, is
"Digestion, Diet, and Disease" The red color often identified as
"E128" is often a major issue for humans, and should be considered so for our pets.
Tartrazine, (Yellow #5), can possibly be triggering your pet's asthma, as another example. The action of dyes in the body are sometimes
used as a medical tool.
I often wonder why these are not addressed when websites discuss allergies and intolernaces in our pets. Another symptom that is becoming all too common among companion animals is
seizure activity. Keep in mind here that the fact that these dyes were found to be triggers came from testing them on animals and getting the same results so the information should not be deemed invalid because it comes from a human focused website.
While I don't personally consider corn to be a threat in our diets, there is the odd anecdotal information out there that does suggest some people/pets do have a problem, and if that is the case you definitely want to look at
the list of ingredients that may be generated from corn if you are running out of options when trying to detect an allergen.