Adverse Rxns to Food Flashcards
Types of adverse food rxns
- True food allergy
- Food intolerance
Food intolerance
-food idiosyncrasy
-pharmacologic reaction
-metabolic reaction
-food poisoning
-dietary indiscretion
True food allergy
-to diagnose, need immunologic basis of rxn AND elimination diet/challenge
-commonly seen as skin then GI manifestations
What are the most common allergens?
-Proteins
-glycoproteins
What can influence something becoming an allergen?
- Food processing
- allergy can be to one or multiple components
Common dog allergies
-milk
-beef
-soy
-wheat
-oats
-eggs
-chicken
-corn meal
-pork
-yeast
Common cat allergens
-milk
-fish
Protection of GI tract from allergens/antigens
Intestinal barrier prevents most antigens from being absorbed in the gut
-includes tight junctions, proteolysis, peristalsis, surface mucus
Protein absorption in the gut
-about 0.002% protein is absorbed intact
-absorbed protein stimulates the GALT (gut associated lymphoid tissue)
-GALT produced secretory antibodies and systemic hyporesponsiveness (tolerance)
Processing of antigens
- normally, antigens processed by enterocytes or macrophages
-B cells become plasma cells making antibodies against the antigens
-T suppressor cells result in tolerance
**if this fails, than food allergy can result
Potential failures of antigen breakdown
-increased mucosal antigen uptake can occur that bypasses normal processing
-allergy from oral challenge with a damaged gut or by a direct injection of antigen into Peyer’s patch
-IgA deficiency- means lacking in antibodies to bind to antigens
-increased permeability
*increases more when allergy established, resulting in further damage and excess antigen bypassing immune system
-genetic (Irish setters; gluten sensitive enteropathy)
Type I reactions
-east to recognize
-includes IgE mediated mast cell degranulation
-released mediators increase permeability, change motility, stimulate mucus production and chloride secretion
Type 3 rxns vs. Type 4 rxns
Type 3: Immune complex deposition
Type 4: delayed hypersensitivity
Type 3 and Type 4 reactions
-most common
-delay in signs makes it harder to detect that issue is allergic in origin
Allergy clinical signs
-more common in young animals (immature immune system)
-Can be Dermatologic (non seasonal pruritus, miliary dermatitis in cats)
-GI: vomiting, diarrhea, changes in appetite, weight loss
-Rare: asthma, behavioural changes and seizures
How do you approach a chronic enteropathy case?
Establish a baseline (CIBDAI scoring or CCECAI scoring)
-factors more likely related to negative outcomes with treatment
eg. itchy dogs +food responsive= poorer outcome
eg. PLE and IBD dogs= less improvement vs. food responsive dogs
Skin test
Detects IgE directed against an antigen in the skin
-won’t detect other delayed responses
-does not indicate GI issue
-ingested antigens may not be allergens; allergen might be from modification in the gut (eg protein altered in gut)
Measurement of food specific IgE
-measured by RAST or ELISA
-in vitro test
-probably good negative predictor
-but issue because high rate of asymptomatic sensitization
*if positive test, and elimination test incriminates same allergen= strong evidence for true food allergy
Gastroscopic food sensitivity testing
-perform gastric endoscopy
-drip some of antigen on the stomach and monitor rxn (blanching, erythema)
-limited to mast cell mediated immediate responses
Elimination/challenge diets
Cannot be used to differentiate between allergy and food intolerance
-Need to feed antigens that have not been fed for at least 6 mths prior to testing
-typically at least 4 week trial (up to 12wks)
-no treats, vitamins, flavoured medications
After good response, patient is rechallenged with typical foods to see if a rxn occurs, and if it does must restart elimination diet again, If signs clear up, then know you have diagnosed a food sensitivity
What diets can be used for elimination diets?
Protein (elk, fish, rabbit, kangaroo, pinto beans)
Carbohydrates (potato, barley, oat)
Treatment options for food sensitivity
- Maintain a novel diet (many commercial brands, but patients can become allergic to the new diet)
- Hydrolysates (proteins broken down to form no longer allergenic)
- avoid offending antigens
- corticosteroids
Hydrolyzed diets study
Conducted on dogs, checks at 6-12mths and then 3 yrs
-when challenged, 70% relapsed within the week
Protein losing enteropathy & diets
- Initial Diet: 1 part skinless chicken breast, 2 parts rice or potatoes
- switch to very low fat commercial diets
*23 of 33 dogs responded to diet
*a score higher than 9 on CCECAI were less likely to respond
