Food allergy dermatitis Flashcards
Seasonality o food allergy?
- non-seasonal (year round)
Different names for food hypersensitivity
- Adverse food reactions
- Food allergy
- Food intolerance
What are the two categories of adverse food reaction?
- Immune-mediated or non-immune mediated
WHat is cutaneous adverse food reaction?
- Food allergy
- Immune-mediated reaction
What is food intolerance?
- Non-immune mediated reaction, in which the animal is unable to digest or otherwise process a dietary component (diarrhea, loose stools, vomiting) without any dermatologic manifestations (e.g. cutaneous infections, pruritus, etc.)
Examples of food intolerance
- Food poisoning
- Food toxicity
- Idiosyncratic reactions
- Pharmacologic and metabolic food reactions
What hypersensitivity types are potentially involved with food allergy?
- Type I
- Type III
- Type IV
Which hypersensitivities are IgE mediated?
Type I and III
Which hypersensitivities are non-IgE?
- Type IV
Pathogenesis of food allergy
- Exposure to allergens over the course of life, and some animals may develop an immune response against a particular foodstuff that activates one of the immunogenic pathways
- Subsequent ingestion of these dietary antigens results in clinical signs
- Development of immune response (oral tolerance)
- Activation of immunogenic pathways
Gi mucosa - how does it typically handle antigens?
- Antigens broken down by effects of gastric acid, pancreatic, and intestinal enzymes
- GI peristalsis also decreases absorption of possible antigens by increasing GI transit time and removal of the dietary antigens trapped in the intestinal mucus
Why don’t dietary antigens usually cause problems?
- Intestinal mucosa forms a barrier that limits absorption of macromolecules, but it’s not a perfect mechanism
- Absorption of antigens through both normal and abnormal gut have been shown
- Antibodies to food allergens, usually IgG, can also be demonstrated in normal individuals but they don’t result in clinical disease
IgA response and GI antigen presentation
- Upon initial presentation, generally there is an immune response involving IgA which helps reduce the absorption of the antigenic substance
- Immune complexes (antigen and IgA) are transported across hepatocytes, into bile, and recirculated to the intestine
Cell types involved in the immune system in the gut?
- Mast cells and lymphocytes in the lamina propria as well as antigen presenting cells and macrophages
- Goblet cells in mucosal epithelium
- M fold cells sitting on top of Peyer’s patches
- Paneth cells secrete antimicrobial peptides
Which proteins are most frequently implicated in food allergies?
- Heat- and acid-stable glycoproteins with molecular weights of 10,000-30,000 Daltons
What are the most common food allergens in dogs?
- Beef
- Chicken
- Dairy products
- Wheat
- Eggs
- Soy
- Fish
- Lamb
Preformed mediators released by mast cells after binding of an antigen?
- Histamien
- Proteases
- Eosinophil and neutrophilic chemotactic factor
- NFAT (involved in production of cytokines that are pro-inflammatory - IL1, IL4, IL5, and IL13)
- release of leukotrienes and prostaglandin
How old are dogs typically with food allergies?
- Less than 1 year of age (6 months)
- May be older
- Can occur in patients eating the same diet for more than 1-2 years
Sites affected with food allergy?
- Ventral hairless areas (like scabies and atopy)
- Face (atopy)
- Feet (like atopy)
- Peri-anal
- “Ears and rears”
- Axillae and inguinal regions (like atopy)
- Pruritic otitis (like atopy)
- Anal pruritus, anal sacculitis, or tail base (like atopy and flea)
Big dfdx for food allergy?
- Environmental allergies
- Ectoparasites
- Main differentiation has to do with seasonality or not
Other clinical features associated with food allergy?
- Otitis
- Recurrent pyodermas
- GI disease (vomiting, diarrhea, loose stools, increased frequency of bowel movements)
- Vasculitis
- Urticaria
- Erythema multiforme (reaction pattern suggesting hypersensitivity)
Rule outs for sensitive stomach in young animals
- Infectious or parasitic causes
Recurring infections possible with food allergy dermatitis
- Pyoderma
- yeast dermatitis
- Otitis externa
How old are cats with food allergy typically?
- 4-5 years
Are cats with food allergy itchy? If so, where?
- Yes
- Head and neck
Reaction patterns seen in cats with food allergy?
- Miliary dermatitis
- Eosinophilic granuloma complex
Dfdx for pruritus
- Atopic dermatitis
- Drug reactions
- Contact hypersensitivity
- Flea allergy
- Scabies
- Yeast dermatitis
- Endocrine disease
Dfdx for diarrhea
- GI parasites
- IBD
- Protein-losing enteropathy
- GI lymphoma
What lesions are seen with food allergy?
- Similar to atopy
- Erythema (ear pinnae, interdigital, axillae)
- Excoriations
- Crust and scale (r/o pyoderma)
- Alopecia
- Hyperpigmentation
- Lichenification
- Salivary staining
Features of endocrine diseases that may help you differentiate from food allergy?
- Hypothyroidism or Cushing’s
- Middle aged to older more often
- Non-pruritic, recurring infections (pyoderma, yeast dermatitis, recurring otitis)
Are there reliable blood or skin tests for food allergy?
- NO
- These tests exist but are not reliable
What is the best way to diagnose food allergy?
- Elimination diet trial for 5-12 weeks and provocative challenge
- Dr. Mel often uses 6-8 weeks as a “time-frame” to provide clients with an endpoint
- Avoid any flavored medications during this time (oral flea/tick/heartworm preventatives and use topical products like Advantage Multi or REvolution or Bravecto)
Which medications commonly given are not okay for animals with food allergies?
- Rimadyl (beef flavored)
- Proin (chicken flavor)
What is important to find out for a successful feeding trial?
- Dietary history
What often gets in the way of feeding trials being successful?
- Client compliance!
- Remember the spouse, children, and co-workers
Oral medications to consider when excluding things for a diet trial
- Vitamins
- Supplements
- Medications (Heartworm, flea, arthritis, urinary incontinence)
- Pill treats
- Dental products
How to relieve pruritus for food allergy?
- Corticosteroids
- Apoquel
- Cytopoint
What should you think if corticosteroids don’t work to relieve itchiness?
- Think food allergies
Types of diets used for feeding trials
- Homemade
- Novel protein
- Hydrolyzed
Reminder: most common allergens?
- Chicken
- beef
- Dairy products
- Wheat
- Eggs
- Fish
What is the gold standard for feeding trials? Why?
- Homemade and raw diets
- Complete control of ingredients
- Antigenicity due to processing
Examples of novel protein diets
- Rabbit
- Kangaroo
- Venison
- Duck
- He likes this best
Taxonomic relationships to consider with novel protein
- Chicken/poultry may mean don’t pick duck as the novel protein
What might you not want to pick if suspect allergy to chicken?
- Duck
What might you not want to pick if suspect an allergy to beef?
- Venison
What are the most novel proteins?
- Rabbit and kangaroo
How do hydrolyzed diets work?
- Peptide bonds in amino acid chains are broken to generate smaller fragments
- Reduce allergenicity
- Improve digestibility
- Molecular weight less than 10,000 daltons (doesn’t allow mast cell degranulation)
Do hydrolyzed protein diets have to be novel necessarily?
- No, not necessarily
Brands of hydrolyzed diet
- Royal Canin (Ultamino, PS, HP which is soy and brewers rice)
- Hills (Z/d and z/d ultra which is chicken liver)
- Purina (HA which is soy)
What’s the difference between partial and complete hydrolyzed diets?
- All diets available right now that are hydrolyzed are only partially hydrolyzed
- This means that molecular weight of some of the proteins will be >10K daltons which can still cause some mast cell degranulation
- Ultimately might not be the best option for a one-time feeding trial
Dermatology consensus for hydrolyzed proteins
- Hydrolyzed diets helpful for diagnosis
- Avoid when native protein is suspected
- Dogs may show clinical signs with hydrolyzed diets
- Repeat diet trial may be necessary
What is royal canin ultamino?
- Short chains of amino acids
- Protein source is feather meal hydrosylate
- Contains zeolite for colon health and stool quality
- protein source is a sustainable, hydrolyzed poultry by-product aggregate
hill’s z/d vs Ultramino
- Hill’s is chicken liver hydrolysate
- 78% peptides below 1000D; 7% >5,000Da
Ultamino is from poultry feather
- 95% of peptides below 1000 Da (88% single AA)
- 99% peptides in final product below 6000D
- MUCH more hydrolyzed in general
Conclusions from RC ultamino vs Hill’s z/d study
- RCU did not induce pruritus flares
- HZD caused a moderate flare in 4/10
- Previous studies reveal 20-50% of dogs can react to hydrolyzed diets containing a known allergen
Grain free (corn and other grains) reality check
- Described as low quality filler
- Implicated as the culprit with food allergies by competitor food companies
- Few veterinary dermatologists and nutritionists believe corn is highly allergenic
- Grain provides a nutritious source of carbs and essential amino and fatty acids for the skin
Over the counter diets characteristics
- Often grain free
- Limited ingredients
- High quality
- Expensive
- Are they as labeled?
Are OTC diets useful for diet trials?
- OTC diets contained food proteins not listed in the ingredient list
- Not made under sterile conditions so cross-contamination is huge
- prescription diets recommended for feeding trials
Where does cross-contamination occur in diets?
- Grain and meat are transported by rail or truck
- Transportation vehicles and/or equipment not thoroughly cleaned
- Unprotected piles of freeze dried meal ingredients (allowable within reason by AAFCO)
What do small companies rely on that may lead to cross-contamination/
- Formulation
- Ingredient supply
- Packaging
- Quality control
WHat is his canine diagnostic approach?
- Pruritus?
- Age of onset
- Seasonal vs non-seasonal
- Infections in skin or ear?
- GI symptoms?
- Derm exam for pyoderma and otitis
If it’s young and not itchy what should you think?
- Food allergies
Treatments for pyoderma and for how long?
- Cephalexin, Simplicef, Convenia, or Clavamox (with cephalexin dose)
- Ideally for 30 days
- Use of 2nd tier antibiotics only based on C/S if using
Treatment for otitis (bacterial cocci, yeast, or both) associated with food allergy?
- Otomax
- Miconazole/dex
- Osurnia
Medications to tamp down pruritus in food allergy patients?
- Cytopoint
- Apoquel
- Temaril-P
Food trial for dogs that he chooses
- Royal canine rabbit dry
- Royal canin rabbit cans for pill pockets
- Apples
- Carrots
- Baked sweet potato
- He does this for 6-8 weeks
Future novel protein sources
- Insects
- microalgae
- Seaweed
What diets may be best for long-term maintenance?
- Hydrolyzed diets are more nutritionally balanced, more sustainable, and less likely to go on backorder
Why avoid prescription duck based diets or venison?
- Duck can react with chicken; venison with beef
Why avoid fish based diets?
- Cheap proteins, generally found in many OTC commercial diets
- QHite fish/salmon=fish
What is hydrolyzation?
- Process where peptides bond in the amino acid chains are broken to generate smaller peptide fragments from the protein molecule in order to reduce allergenicity and increase digestibility
Cons of home cooked diets
- Time consuming, may not be nutritionally balanced; may need to consult a veterinary nutritionist
How do you end a feeding trials?
- Provocative challenge
- Return patient back to previous foods to determine if reaction occurs
- Can take hours, days, or up to 2 weeks
- Best to add/introduce items/proteins 1 at a time
