Food Allergy & Contact Allergy (Marsella)

Question 1

Define food allergy

Answer 1

• Non-seasonal
• Pruritic skin disorder
• Associated w/ ingestion of substance found in animal’s diet

Question 2

Immunologically mediated reaction to food

Answer 2

True allergy. Any type of hypersensitivity

Question 3

Non-immunologically mediated reactions to food

Answer 3

• Food intolerance
• Metabolic effect
• Pharmacologic effect
  
  • Toxic effect

Question 4

Characteristics of food allergens

Answer 4

• Proteins
• Able to trigger immune response

Question 5

Factors that determine allergenic potential of food

Answer 5

• Molecular complexity
• Solubility
• Stability
• Concentration

Question 6

Pathogenesis of food allergy

Answer 6

Typically type I (can also be type II, III, IV)

Question 7

Predilection of clinical disease in the dog for food allergy

Answer 7

• Breed predilection possibly
• Any age, any gender
• Change in diet is not necessary

Question 8

Common food allergens in the dog

Answer 8

• Beef
• Eggs
• Soybean

Question 9

Distribution of pruritis in canine food allergy

Answer 9

• Face
• Feet
• Ears
• Perineal
• Generalized

Question 10

Clinical signs of food allergy

Answer 10

• Recurrent, moist dermatitis
• Recurrent urticaria (hives)
• Papular, macular eruption
• 2º lesions (scaling, lichenification, hyperpigmentation, excoriations, crusting)

Question 11

Non-dermatologic signs of food allergy

Answer 11

• GI symptoms (15% of cases)
  
  • >4 bowel movements/day
  • Vomit/Diarrhea
  • Bloating, cramping

Question 12

Feline food allergy

Answer 12

• Miliary dermatitis
• Head & face pruritis
• Self-induced alopecia
• Eosinophilic granuloma complex
• Concurrent GI signs

Question 13

Eosinophilic granuloma complex

Answer 13

• Indolent ulcer
• Eosinophilic granuloma
• Eosinophilic plaque

(feline food allergy)

Question 14

Diagnosis of food allergy

Answer 14

• Food trial
• Intradermal skin test
• Serology

Question 15

Food trial

Answer 15

• Novel source of protein & carb
• No chewable meds, treats
• Clear infections before trial
• Control concurrent allergies
• Monitor for pruritis & recurrance of infections

Question 16

Novel proteins

Answer 16

Lamb, venison, duck, rabbit, kangaroo, lentils, salmon

Question 17

Hydrolyzed diets

Answer 17

• Minimum molecular wt to cause cross linking of IgE
• Limitations
  
  • Only applies to type I hypersensitivity
  • Small peptides can aggregate to appropriate size
  • Incr. risk of type IV hypersensitivity

Question 18

Food allergy therapy

Answer 18

• Avoidance
• Home-cooked diets

Question 19

Causes of contact dermatitis

Answer 19

• Irritant
• Allergic
  
  • Type IV hypersensitivity

Question 20

Irritant contact dermatitis

Answer 20

• All animals in contact are affected
• Chemical
• Physical
• Signs develop at 1st exposure (vesicles, pain, +/- pruritis)

Question 21

Contact allergic dermatitis

Answer 21

• Type IV hypersensitivity
• Clinical signs do NOT develop at 1st exposure (sensitizaiton period of 2-6 mos)
• Usually only one animal affected
• Pruritis, papules

Question 22

Contact allergens

Answer 22

Small-size molecules that can penetrate skin barrier (haptens)

Question 23

Clinical signs of contact allergy

Answer 23

Pruritic papular eruption of face, feet, groin, axillae

Question 24

Contact allergy diagnosis

Answer 24

• Resolution of clinical signs w/ avoidance (7-10 days)
• Relapse after re-exposure (1-3 days)
• Patch test

Question 25

Patch test

Answer 25

• shave area on thorax 24 hrs before
• Apply suspect substance and negative control
• Bandage
• Read after 48 hrs

Question 26

Contact allergy therapy

Answer 26

• Avoidance
• Glucocorticoids
• Pentoxifylline (48 hrs prior to exposure)
• (Hyposensitization NOT effective)