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RUSVM SAM 2 > Pruritus 2- Food Allergic Derm And Contact Dermaitits > Flashcards

Pruritus 2- Food Allergic Derm And Contact Dermaitits Flashcards

1
Q

What is the difference between food allergy, dietary intolerance, and food anaphylaxis?

A

Food allergy — immune response

Dietary intolerance — no immune response

Food anaphylaxis — systemic involvement

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2
Q

What are the types of dietary intolerance ?

A

Food idiosyncrasy - resembles allergy but no immune response

Food poisoning - non immune reponse to food or toxin

Pharmacological rxn — drug like effect of food on host

Food indiscretion — gluttony, pica or indigestible material

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3
Q

T/f: food intolerance occurs following the first exposure to food/additive/toxin

A

True

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4
Q

What is food anaphylaxis?.

A

Acute food allergy

  • systemic consequence
  • resp distress
  • vascular collapse
  • urticaria
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5
Q

T/F: food allergies are relatively rare

A

True

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6
Q

What are the most common food allergens

A

Protein (most commonly beef protein in cats and dogs)

Glycoproteins - water soluble (10,000-70,000 Da)

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7
Q

Food allergy is a type __ hypersensitivity rxn

A

1

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8
Q

What is part of the normal innate immune response to food antigens?

A

Anatomical - mucosa of intestine

Physiological

  • pH
  • mucous protective layer
  • peristalsis
  • body temp

Cellular

  • neutrophil
  • macrophage
  • NK cells
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9
Q

What is part of the normal adaptive immunity response to food antigens

A

Cell mediated - T lymphocyte

Humoral : B lymphocyte , plasma cell, and immunoglobulins

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10
Q

Normally food allergens are prevented by passing through the intestinal wall barrier by.. ?

A

Innate immune system and IgA antibodies in mucous layer

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11
Q

What cells of the intestine are capable of capturing food antigens?

A

Macrophages
Dendritic cells
M-cell (associated with GALT)
Enterocytes

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12
Q

T1 helper cells activate what repsonse ?

A

Cell mediated response —> T lymphocyte proliferation and macrophage activation

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13
Q

T2 helper cells activate what response?

A

Humoral response —> B lymphocyte proliferation and immunoglobulin production

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14
Q

What are all the possible hypersensitivity rxns that a food allergy can cause, most common to least common?

A

Type 1 > type 4 > type 3

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15
Q

What is the pathogenesis of food allergy in a type 1 hypersensitivity rxn?

A

Allergen -> activate TH2 —> activated B lymphocyte –> plasma cell —> produced IgE —> bind mast cells

Mast cells release
-histamine, protease, chemotatic factors, prostaglandins, leukotrienes, and cytokines

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16
Q

Clinical signs associated with type 1 hypersensitivity from food allergy?

A

Vasoactive amines cause
—>Pruritus
—>Hyperemia
—>Angioedema

Local rxn in GIT
—> diarrhea
—> abdominal discomfort
—> vomiting

Severe rxn causes
—> anaphylaxis, angioedema, hypotension, respiratory distress

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17
Q

Pathogenesis of type 4 hypersensitivity cause by food allergy?

A

Food allergen —> activate TH1 —> T lymphocyte proliferation —> release of chemotaxic factors (attracts macrophages) —> degranulation

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18
Q

What are the 3 most common hypersensitivity skin diseases in adult dogs from most to least?

A

Flea > atopy > food

19
Q

What are the 3 most common hypersensitivity skin diseases in dogs less than 6months, from most to least?

A

Flea > food > atopy

20
Q

Breeds predisposed to food allergy?

A 
Labrador retriever 
Collies 
Miniature schauzers 
Spaniel 
Chinese shar-pei 
Boxer
Dashunds
GSD 
West highland white terrier
21
Q

T/F: food allergies are non-seasonal

A

True

Although they can flare up more in summer when wet and humid —> predispose to secondary bacterial infection

22
Q

Types of lesions seen with food allergy?

A

Primary

  • papule
  • erythema
  • wheal
  • plaques

Secondary

  • excoriation
  • crusting
  • hyperpigmentation/lichenification
  • ulcer due to deep scratches
23
Q

Where are food allergy lesions usually localized in dog?

A

Muzzle, ear, distal limb/ paw, axillary, groin

24
Q

Where are food allergy lesions usually localized in cats?

A

Head, face
Pinnae
Neck

25
Q

What is the ONLY way to diagnose food allergy dermatitis?

A

Positive response to an elimination diet
—> 95% of dogs improve within 3 weeks

biggest limitation - owner compliance

26
Q

T/F: intradermal skin testing is useful in determining food allergy

A

False

Very inaccurate - low sensitivity

27
Q

T/F: ELISA serology shows good correlation between positive serology result and the antigen causing reaction

A

False

—> often false positive
-high sensitivity and low specificity

28
Q

What is colonoscopy allergen provocation?

A

Allergens are injected into the mucosa of the colon

Observation made of wheal or flare reaction
** more sensitive than interdermal or ELISA serology testing**

Technically challenging
Cost is thigh

29
Q

What are the three dietary options available for dogs with food allergies?

A

Low allergy commercial diet (novel proteins and carbohydrate sources)

Homemade hypoallergenic diet (novel proteins, carbohydrate, and free of additives)

Hydrolyzed protein diet (eg z/d)

30
Q

For homemade hypoallergenic diets, which carbohydrates appear to be least allergenic?

A

Tofu and brown rice

31
Q

What is a hydrolyzed protein diet?

A

Proteins hydrolyzed into small particles

The smaller the particle the less antigenic they become —> should be less than 10,000Da

These small particles cannot bind to IgE on mast cells => degranulation is prevented

32
Q

How are hydrolyzed protein diets made?

A

Antigenicity of protein is determined by structure
—> disrupt 3D structure
—> alter amino acid side chains
—> cleave peptide bond

Done with
—heat or pH
—enzymatic hydrolysis
—ultrafiltration

33
Q

What is the difference between hills z/d ultra allergen free and hills z/d low allergen ?

A

Z/d ultra —> only have proteins under 3000Da

Z/d low allergen —> average 3000Da but can have more of a range

34
Q

What is the disadvantage of hydrolyzed protein diets?

A

Low palatability

35
Q

How do you treat secondary skin infections due to food allergy?

A

Antibiotics for bacterial dermatitis

  • cephalexin
  • pyostat/pyoderm

Antifungals prep for Malassezia spp

  • Niz shampoo
  • pyostat/pyoderm
  • imaverol dips
36
Q

How will you treat secondary pruritus due to food allergy?

A

Only if unresponsive to topical washes

  • prednisolone
  • topical steroid preps —> hydrocortisone
37
Q

A minimum of ___ antihistamines should be tried before before a failure of response to antihistamines can be determined for pruritus?

A

3

Chlorphenamine 
Diphenhydramine hydrochloride 
Clemastine 
Hydroxyzine 
Terfendine
38
Q

What is the prognosis for food allergy dermatitis?

A

Excellent if dog responds to diet

Cannot exclude food allergy if does not respond

  • reaction to additive/protein
  • owner compliance
  • try another diet
39
Q

Urticaria and angioedema is an allergic/ non-allergic response to….?

A 
Drugs 
Insect stings/bites 
Food 
Vaccine 
Plant 
Heat/cold 
Sunlight 
Stress
40
Q

Clinical signs of urticaria and angioedema ??

A

Sudden onset of local or generalized wheals, oedematous swelling

Dyspnea
Anaphylaxis

Pruritus

41
Q

Treatment for urticaria and angioedema ?

A

Remove antigen

Injectable antihistamine (mepyramine maleate, diphenhydramine)

Injectable steroids - corticosteroids

Dyspnea may require Adrenalin

42
Q

What is contact dermatitis

A

Prolonged exposure to a offending surface —> type 4 hypersensitivity rxn

extremely rare

43
Q

Clinical signs of contact dermatitis?

A

Intensely pruritic

Papule, erythema, macule, alopecia, plaques, vesicles, excoriation

Hyperpigmentation and lichenification
Secondary infection

Lips if food bowl is caused
Neck if collar

44
Q

Treatment for contact dermatitis

A

Identify allergen

Treat secondary infections
Mechanical barriers

Poorly steroid responsive

RUSVM SAM 2 (44 decks)

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