DERMATOLOGY
included in the list of likely allergens.
What would we feed in a food trial and why?
Hydrolysed protein diets are currently the best way to
investigate the role of a dietary allergen in pruritic skin
disease.
The quality of the hydrolysed diet is very important
The more completely hydrolysed the protein
source, the better the quality of the trial will be. The
quality of the diet is crucial as contamination of the
prepared food during production has been shown to
compromise the diet. It has also been shown in some
cases that the label claim on the food bag does not
always match the protein source of the diet in the bag.
These factors must weigh on the clinician’s choice of a
diet – the higher the quality of the diet used, the more
likely the outcome of a trial are to be trustworthy.
For how long do we feed the test diet?
80% of dogs with food allergies can be diagnosed
with a 5 week trial. Six weeks are necessary to catch
the same proportion of cats. By 8 weeks, around
90% of dogs and cats that are food allergic will show
a response. For this reason we traditionally conduct
trials for 8 weeks.
What advice do we give to owners about con-
ducting a food trial?
Satisfying dermatology practice depends very
heavily on excellent communication with the client.
Frustration with helping owners with itchy pets can
very often be attributed to poor communication, a
hurried consultation with inadequate information
provided to the owner to give them the opportunity
to come on board for what is going to require great
compliance over a long time and will invariable cost
more than what they were bargaining. A poorly
conducted food trial is a huge waste of money time
and the owners energy.
Here is a suggested discussion framework to use
when trying to help pet owners understand how a
food trail should be done:
1. Redefine the owner’s definition of ‘success’. To
them success invariable means, ‘I fed this diet
and the skin got better’. That is not my definition
of a successful food trial. Success to us is, ‘I fed
this diet in such a way as to be sure that after
the completion of the trial, the response I see
in the skin (improved or not), is believable’. A
well conducted trial provides results that can be
trusted – not a particular result.
2. Always help owners decide if a food trial is even
doable in their home environments. A dog that
comes from a large farm with 10 other dogs that
are all fed together may never allow a proper trial.
3. Help owners decide of they will feed all the dogs
in the home the prescribed diet or will they feed
the affected dog in isolation. Remember, even
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Issue 02 | MAY 2019 | 26
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licking the empty food bowls of other dogs
negates the food trial.
If there are cats in the environment, their food
must be well out of reach of the dog on trial.
ALL treats must STOP. Here it important to
explore what owners do to treat their dogs and
they may not appreciate what you mean by
‘treats’ (biscuits, biltong or droëwors when watch
the Saturday game on TV, a bit of fat from the
Sunday afternoon braai, to small piece of cheese
at bedtime etc)
All flavoured medication must be stopped for the
trial duration. The only medications that should
be allowed are those used to treat serious medical
disease (such as drugs used for heart failure or
seizure control).
Avoid starting a trial over Christmas or other times
of the year when there is a lot of food around a
family home. Avoid starting a trial that will span a
holiday season for the owners. The pets owners
must be the ones fully invested in the trial; you
cannot expect a sitter to conduct this.
Dogs love small children because they leave a
trail of half eaten hotdogs, popcorn and chips
that they delight in vacuuming up. This destroys a
trial. Kids parties are the worst!
Anyone who lives or works on the property (in
a flatlet, house or garden help) must be fully
informed and on board with what is happening.
Some dogs love to lick the dirty dishes in the
open dishwasher. This is a no-no.
Care should be taken to prevent access to food
thrown away in the bin or on a compost heap.
After this discussion, owners usually understand the
seriousness of the trial and that a well conducted trial
will almost always result in some level of domestic
upheaval.
Because many of these pets are really pruritic when
we start the diet trial, I will almost always provide
some form of oral and/or topical treatment to make
their lives more comfortable for the first 6 weeks of
the diet trial. The last 2 weeks must be free of all drug
use (except shampoo treatment) so that the effect of
the diet alone can be unmasked and assessed. I will
commonly use oral prednisone or prednisolone at a
low dose to at least provide some relief. Oclacitinib
(Apoquel®, Zoetis) can also be used very effectively
for this purpose.
How do we judge response?
Assessing response to the diet trial on a daily basis is
important. I use a 10-point scale with 0 being a normal
dog and 10 being the score that would be given for
the worst the owners have ever seen the skin. It is
unimportant to me exactly what a 3 or a 7 may mean
– what is more important to me is the trend of these
scores over time. Owners will have a way of judging
the seriousness of the skin disease in their own heads
and trying to teach them to adapt this to a strict set of