Derm 8 - allergies Flashcards
what do we rule out before considering allergies?
- rule out parasites and secondary microbial dermatitis first
rule outs for allergies in the non-seasonal dog
- adverse food reaction and environmental allergy
- don’t forget - can be multifactorial and often is (>50% in some studies)
first priority for itchy dog
control microbes - 67% of recurrent pyoderma is a result of hypersensitivity
> microbes contribute to persistent inflammation
> Without control of these “flare factors”, treatment is bound to fail
adverse food reactions in dogs are implicated in what proportion of cases of pruritis? what proporiton of dogs with any type of allergic skin disease?
what proportion of skin cases overall?
- 18% of all cases of pruritus
- 20% of dogs with any type of allergic skin disease
- 6% of all skin cases
prevalence of adverse food reactions in cats:
- proportion of total skin cases, cases of allergic skin disease, and cases of self-trauma
- 5% of all feline skin cases
- 10% of cats with any type of allergic skin disease
- plays a role in over 50% of cases of feline self trauma
food allergy - seasonal or not
a pure food allergy should be non-seasonal
utility of serum tests for food allergies
not reliable, low accuracy
utility of saliva testing for food allergy identification
- no better than chance, results not reproducible
age of onset for AFRs
adverse food reactions do not seem to have the same time constraints as environmental allergies
and can be seen as well in the very young or the very old as well
ideal test for food allergies
food trials
> Blood or saliva tests are not recommended to diagnose a food allergy
most important aspects of elimination diet trial
- owners must be strict
- adequate trial duration
> 90% of dogs and cats are in remission by 8 weeks
will raw vs cooked food make a difference for allergies?
Theory of allergies: You are not allergic to a “method of preparation”
raw food diets and antimicrobial resistance
raw feeding is associated with carriage of ABR (antibacterial resistant) E. coli in dogs even at 16 weeks of age and that bacteria carried by puppies are shared with humans
common cross reactions for ingredients, when planing new diet
Fish with Each other
Milk and Beef
Pollens and Fruits
Beef, lamb and venison cross react in vitro
Chicken with turkey, pheasant, quail
çhicken and fish???????OMG!!
fish-chicken syndrome - what is it? conclusions?
Sera cross reactivity has been identified between
chicken, white fish (haddock and cod) and salmon
> 9 cross reactive proteins
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Conclusion: “Still needs to be determined if the identified cross reactive chicken-fish allergens is the
cause of clinical allergy in dogs that react to at least 2
of these common food sources
utility of hydolyzed diets for allergies
- Up to 50% of dogs with CAFR exhibit increases in clinical signs after ingesting partial hydrolysates derived from foods to which they were hypersensitive…
- A variable proportion of dogs with
CAFR will exhibit a worsening of
clinical signs when fed partial
hydrolysates……
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Conclusion:
At this time, hydrolysate-containing diets are
probably best used in dogs suspected not to be hypersensitive to their individual components
use of hydrolyzed feathers? reactivity?
IgE cross reactivity of chicken to duck and turkey demonstrated but not to ultra hydrolyzed feathers
are commercial single protein diets trustworthy for diet elimination trials
- some may have ingredients not on the label…
> When choosing a commercial elimination diet, choose a reputable company that checks for cross contamination
the perfect hypoallergenic diet is…
The diet that doesn’t contain the ingredient(s) to which
the dog is allergic
when performing an elimination trial, what do we do once the patient feels better?
- step 2
- step 3
Step 2:
Dietary challenge - “party time”
- confirm that the diet made the difference!
- eat a variety of things and see what happens
- be sure to warn family members about the potential for relapse
> if relapse, go back to test diet until better
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Step 3:
Dietary provocation
- Try to identify the individual offending ingredients
- add one ingredient at a time
> watch out for seasonal complications
lesion distribution of atopic dermatitis vs food allergies vs Malassezia
AD/food are the same:
affect paws, arm pits, groin region, area around the mouth, around the eyes, and under the ears
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Malassezia is very similar:
affects paws, groin region, armpits, around the mouth, under ears
> but also affects ventral neck
> doesn’t affect eyes like AD/food
summmary of important steps for a food eliminatino trial:
- Choose a diet
- The diet must be performed strictly
- Decide on the appropriate diet > select a protein, very different than one previously fed (eg. rabbit, alligator, kangaroo)
- remember potential for cross reactions - Control concurrent microbes – I will often have patients on concurrent antibiotic (and sometimes antifungal) medications
- Control for parasites – don’t let a flea mess up your test
- Control for Environment
- Many patients will have a concurrent adverse food reaction and environmental hypersensitivity. Whenever possible, it is best to perform the diet when there is minimal exposure to seasonal pollens (I try to do my dietary trials in the winter) - Trial length – remission in more than 90% of dogs and cats by 8 weeks; but can take as much as 12 weeks
- Challenge. Confirm that the diet made the difference
- Provoke (also called re-challenge trials). Try to identify the individual offending ingredients
Diagnostic criteria for Atopic Dermatitis in the dog
fulfillment of 5 of these criteria met with a high sensitivity and specificity:
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1. Age at onset <3 years
2. Mostly indoor
3. Corticosteroid-responsive pruritus
4. Chronic or recurrent yeast infections (include bacteria - SW)
5. Affected front feet
6. Affected ear pinnae
7. Non-affected ear margins
8. Non-affected dorso-lumbar area
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Two criteria were highly associated with non-CAD conditions: affected ear margins and affected dorso-lumbar area.
reliability of different sets of criteria for diagnosing atopic dermatitis in canines? what do we need to take into account?
- no set of criteria should be considered the gold standard
- that the diagnosis of atopic dermatitis should be made using history, clinical presentation and by ruling out similar presenting disease; in particular, parasitic and other infectious diseases.
major reason for treatment failure in referral cases
lack of recognition of the multifactorial nature of the disease
