Page 1483 - Clinical Small Animal Internal Medicine

161 Cutaneous Adverse Food Reactions 1421

Diagnosis cross‐linking of IgE on the surface of inflammatory cells
VetBooks.ir Although serum testing for food allergen‐specific IgE is less likely, and thus these diets can be considered truly
“hypoallergenic.” Hydrolyzed diets and selected protein
diets do not lead to remission in all animals with an adverse
offered in many countries, there is no evidence that this
test has any value in the diagnosis of adverse food food reaction and thus are the second best option for diag-
reactions. In all previous publications, numerous false‐ nosing the condition. The exact reason for this decreased
positive and false‐negative reactions were detected, when efficacy is not known at this time, but may relate to the
comparing test results with clinical rechallenges. In one presence of a concurrent allergic condition, cross‐
recent study, false‐negative reactions were less likely. reactivities or adverse food reactions that are not immune
However, at this time there is unanimous agreement mediated in the first place. However, these diets are often
amongst dermatologists worldwide that the only reliable ideally suited for long‐term maintenance, once the diagno-
way to diagnose an adverse food reaction is an elimina- sis is made and patients have been shown to tolerate them.
tion diet with food stuffs previously not fed to the patient. If it is not possible for owners to feed a previously
unfed protein or carbohydrate source, either because
what is available is simply too costly (which may be rele-
Choice of Elimination Diet
vant for owners of large dogs) or because dogs or cats
In dogs, one protein source and one carbohydrate source have been fed a wide variety of foods in the past, then it
not previously fed will be used exclusively; in cats, feed- is sensible to choose the food sources the animals have
ing only the protein source increases palatibility and seen the least or only in the more distant past, when clin-
compliance. Thus, it is important to obtain a reliable and ical signs were not present. In one Dutch study of dogs
detailed feeding history for the patient as well as the with an adverse food reaction being fed three commer-
ingredient lists of commercial foods fed in the past. cial protein diets, no dog responded to all of the diets but
Ideally, the food should be home‐cooked to assure that almost all dogs responded to at least one of them. Thus,
only the selected food stuffs are used. This is even more performing two or three commercial diet trials in dogs
important after evidence has been published that many with a suspected adverse food reaction may be useful.
dog foods may include food sources not listed on the
label. However, convincing owners to cook for their pets Duration and Execution of the Diet
for several weeks may be more difficult nowadays than it
used to be half a century ago. In addition, home‐cooked The ideal duration of an elimination diet is controversial.
diets are rarely balanced, which typically does not lead to In a study evaluating the duration until clinical remission
clinical problems in adult dogs on a deficient diet for in 51 dogs with adverse food reaction, less than a quarter
only a short time such as a month or two. However, if of the dogs responded within the first three weeks, a
home‐cooked diets are fed for extended time periods or further half after 4–6 weeks, 10 dogs after 7–8 weeks,
if the patient is a young dog or cat still growing, care and three dogs after 9–10 weeks. However, although the
must be taken to seek advice from a nutritionist and time to complete remission can be extended, most dogs
balance the diet to avoid nutritional deficiencies. will start improving within the first 6–8 weeks and if a
To what degree cross‐reactivities between related patient shows no clinical improvement on an appropri-
allergens (for example, beef and mutton or cow’s milk) ate elimination diet within that time, the author consid-
are clinically relevant in the dog and cat is currently ers adverse food reaction ruled out. One has to keep in
unclear. One study showed in vitro evidence of reactivity mind that the longer the trial duration, the higher the
of most dog sera with specific IgE antibodies against likelihood for lack of owner compliance.
bovine IgG present in cow’s milk and lamb and beef In most patients, a gradual switch from the original diet to
extract. Studies evaluating clinical cross‐reactivity are the elimination diet over a few days will help with compli-
rare and so far have not confirmed those findings. The ance as well as gastrointestinal complications, particularly
author prefers to use food sources removed as far as pos- in finicky dogs and in cats. In dogs, owners are the limiting
sible from the previously fed antigens; for example, ani- factor for most unsuccessful diet trials. However, cats often
mals fed predominantly meat such as beef, mutton or prove more difficult and due to the threat of hepatic lipido-
pork will receive poultry proteins such as duck or goose sis after several days of refusing to accept the diet, particu-
and pets on a predominantly chicken‐based food will be larly in obese cats, it is not uncommon to try a number of
recommended goat, buffalo or reindeer. feeding options before a suitable diet is identified.
If owners cannot be convinced to cook for their pets, The most important detail to relate to the owners is
commercial diets with selected protein and carbohydrate the need for maximal compliance. Even small amounts of
sources are sold by many companies. Furthermore, food antigens fed infrequently can trigger pruritus and
hydrolyzed diets are also available. These diets contain thus mask improvement, so flavored medications or
hydrolyzed proteins and their small sizes make treats such as rawhide, pig’s ears, and others must be