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Dermatology > Food allergy dermatitis > Flashcards

Food allergy dermatitis Flashcards

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Dermatology Board Prep flashcards
1
Q

Seasonality o food allergy?

A
  • non-seasonal (year round)
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2
Q

Different names for food hypersensitivity

A
  • Adverse food reactions
  • Food allergy
  • Food intolerance
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3
Q

What are the two categories of adverse food reaction?

A
    • Immune-mediated or non-immune mediated
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4
Q

WHat is cutaneous adverse food reaction?

A
  • Food allergy

- Immune-mediated reaction

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5
Q

What is food intolerance?

A
  • 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.)
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6
Q

Examples of food intolerance

A
  • Food poisoning
  • Food toxicity
  • Idiosyncratic reactions
  • Pharmacologic and metabolic food reactions
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7
Q

What hypersensitivity types are potentially involved with food allergy?

A
  • Type I
  • Type III
  • Type IV
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8
Q

Which hypersensitivities are IgE mediated?

A

Type I and III

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9
Q

Which hypersensitivities are non-IgE?

A
  • Type IV
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10
Q

Pathogenesis of food allergy

A
  • 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
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11
Q

Gi mucosa - how does it typically handle antigens?

A
  • 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
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12
Q

Why don’t dietary antigens usually cause problems?

A
  • 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
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13
Q

IgA response and GI antigen presentation

A
  • 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
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14
Q

Cell types involved in the immune system in the gut?

A
  • 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
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15
Q

Which proteins are most frequently implicated in food allergies?

A
  • Heat- and acid-stable glycoproteins with molecular weights of 10,000-30,000 Daltons
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16
Q

What are the most common food allergens in dogs?

A
  1. Beef
  2. Chicken
  3. Dairy products
  4. Wheat
  5. Eggs
  6. Soy
  7. Fish
  8. Lamb
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17
Q

Preformed mediators released by mast cells after binding of an antigen?

A
  • 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
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18
Q

How old are dogs typically with food allergies?

A
  • 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
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19
Q

Sites affected with food allergy?

A
  • 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)
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20
Q

Big dfdx for food allergy?

A
  • Environmental allergies
  • Ectoparasites
  • Main differentiation has to do with seasonality or not
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21
Q

Other clinical features associated with food allergy?

A
  • Otitis
  • Recurrent pyodermas
  • GI disease (vomiting, diarrhea, loose stools, increased frequency of bowel movements)
  • Vasculitis
  • Urticaria
  • Erythema multiforme (reaction pattern suggesting hypersensitivity)
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22
Q

Rule outs for sensitive stomach in young animals

A
  • Infectious or parasitic causes
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23
Q

Recurring infections possible with food allergy dermatitis

A
  • Pyoderma
  • yeast dermatitis
  • Otitis externa
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24
Q

How old are cats with food allergy typically?

A
  • 4-5 years
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25
Q

Are cats with food allergy itchy? If so, where?

A
  • Yes

- Head and neck

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26
Q

Reaction patterns seen in cats with food allergy?

A
  • Miliary dermatitis

- Eosinophilic granuloma complex

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27
Q

Dfdx for pruritus

A
  • Atopic dermatitis
  • Drug reactions
  • Contact hypersensitivity
  • Flea allergy
  • Scabies
  • Yeast dermatitis
  • Endocrine disease
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28
Q

Dfdx for diarrhea

A
  • GI parasites
  • IBD
  • Protein-losing enteropathy
  • GI lymphoma
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29
Q

What lesions are seen with food allergy?

A
  • Similar to atopy
  • Erythema (ear pinnae, interdigital, axillae)
  • Excoriations
  • Crust and scale (r/o pyoderma)
  • Alopecia
  • Hyperpigmentation
  • Lichenification
  • Salivary staining
30
Q

Features of endocrine diseases that may help you differentiate from food allergy?

A
  • Hypothyroidism or Cushing’s
  • Middle aged to older more often
  • Non-pruritic, recurring infections (pyoderma, yeast dermatitis, recurring otitis)
31
Q

Are there reliable blood or skin tests for food allergy?

A
  • NO

- These tests exist but are not reliable

32
Q

What is the best way to diagnose food allergy?

A
  • 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)
33
Q

Which medications commonly given are not okay for animals with food allergies?

A
  • Rimadyl (beef flavored)

- Proin (chicken flavor)

34
Q

What is important to find out for a successful feeding trial?

A
  • Dietary history
35
Q

What often gets in the way of feeding trials being successful?

A
  • Client compliance!

- Remember the spouse, children, and co-workers

36
Q

Oral medications to consider when excluding things for a diet trial

A
  • Vitamins
  • Supplements
  • Medications (Heartworm, flea, arthritis, urinary incontinence)
  • Pill treats
  • Dental products
37
Q

How to relieve pruritus for food allergy?

A
  • Corticosteroids
  • Apoquel
  • Cytopoint
38
Q

What should you think if corticosteroids don’t work to relieve itchiness?

A
  • Think food allergies
39
Q

Types of diets used for feeding trials

A
  • Homemade
  • Novel protein
  • Hydrolyzed
40
Q

Reminder: most common allergens?

A
  • Chicken
  • beef
  • Dairy products
  • Wheat
  • Eggs
  • Fish
41
Q

What is the gold standard for feeding trials? Why?

A
  • Homemade and raw diets
  • Complete control of ingredients
  • Antigenicity due to processing
42
Q

Examples of novel protein diets

A
  • Rabbit
  • Kangaroo
  • Venison
  • Duck
  • He likes this best
43
Q

Taxonomic relationships to consider with novel protein

A
  • Chicken/poultry may mean don’t pick duck as the novel protein
44
Q

What might you not want to pick if suspect allergy to chicken?

A
  • Duck
45
Q

What might you not want to pick if suspect an allergy to beef?

A
  • Venison
46
Q

What are the most novel proteins?

A
  • Rabbit and kangaroo
47
Q

How do hydrolyzed diets work?

A
  • 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)
48
Q

Do hydrolyzed protein diets have to be novel necessarily?

A
  • No, not necessarily
49
Q

Brands of hydrolyzed diet

A
  • 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)
50
Q

What’s the difference between partial and complete hydrolyzed diets?

A
  • 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
51
Q

Dermatology consensus for hydrolyzed proteins

A
  • 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
52
Q

What is royal canin ultamino?

A
  • 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
53
Q

hill’s z/d vs Ultramino

A
  • 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
54
Q

Conclusions from RC ultamino vs Hill’s z/d study

A
  • 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
55
Q

Grain free (corn and other grains) reality check

A
  • 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
56
Q

Over the counter diets characteristics

A
  • Often grain free
  • Limited ingredients
  • High quality
  • Expensive
  • Are they as labeled?
57
Q

Are OTC diets useful for diet trials?

A
  • 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
58
Q

Where does cross-contamination occur in diets?

A
  • 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)
59
Q

What do small companies rely on that may lead to cross-contamination/

A
  • Formulation
  • Ingredient supply
  • Packaging
  • Quality control
60
Q

WHat is his canine diagnostic approach?

A
  • Pruritus?
  • Age of onset
  • Seasonal vs non-seasonal
  • Infections in skin or ear?
  • GI symptoms?
  • Derm exam for pyoderma and otitis
61
Q

If it’s young and not itchy what should you think?

A
  • Food allergies
62
Q

Treatments for pyoderma and for how long?

A
  • Cephalexin, Simplicef, Convenia, or Clavamox (with cephalexin dose)
  • Ideally for 30 days
  • Use of 2nd tier antibiotics only based on C/S if using
63
Q

Treatment for otitis (bacterial cocci, yeast, or both) associated with food allergy?

A
  • Otomax
  • Miconazole/dex
  • Osurnia
64
Q

Medications to tamp down pruritus in food allergy patients?

A
  • Cytopoint
  • Apoquel
  • Temaril-P
65
Q

Food trial for dogs that he chooses

A
  • Royal canine rabbit dry
  • Royal canin rabbit cans for pill pockets
  • Apples
  • Carrots
  • Baked sweet potato
  • He does this for 6-8 weeks
66
Q

Future novel protein sources

A
  • Insects
  • microalgae
  • Seaweed
67
Q

What diets may be best for long-term maintenance?

A
  • Hydrolyzed diets are more nutritionally balanced, more sustainable, and less likely to go on backorder
68
Q

Why avoid prescription duck based diets or venison?

A
  • Duck can react with chicken; venison with beef
69
Q

Why avoid fish based diets?

A
  • Cheap proteins, generally found in many OTC commercial diets
  • QHite fish/salmon=fish
70
Q

What is hydrolyzation?

A
  • 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
71
Q

Cons of home cooked diets

A
  • Time consuming, may not be nutritionally balanced; may need to consult a veterinary nutritionist
72
Q

How do you end a feeding trials?

A
  • 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

Dermatology (15 decks)

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