food allergy

Question 1

Food Allergy:

Answer 1

an abnormal immunologic response to a food protein

Question 2

Food Intolerance:

Answer 2

 result of nonimmunological mechanisms

Question 3

Food Sensi/vity:

Answer 3

generic term referring to a troublesome reac-on aCer the inges-on of a food

Question 4

Categories Adverse Food Reac-ons •  Immune Mediated:

Answer 4

Food Allergy and Celiac Disease IgE Mediated - anaphylaxis, oral allergy syndrome Non-IgE Mediated – enterocoli-s, food protein-induced proctocoli-s Mixed IgE and non IgE Mediated –, eosinophilic esophagi-s, eosinophilic gastroenteri-s

Question 5

•  Non-Immune Mediated:

Answer 5

Food Intolerance Metabolic – Lactose Intolerance Pharmacologic – Caffeine Toxic – fish toxin Idiopathic - sulfites

Question 6

IgE

Answer 6

key immunoglobin in allergy
  Immunological process in an allergic reac-on involves ac-va-on of the immune system in response to a ‘foreign’ an-gen (protein) and the produc-on and release of adverse reac-ve chemicals that act on body -ssues to produce symptoms of allergy

Question 7

Immunological Process

Answer 7

When a foreign an-gen enters the body, lymphocytes are ac-vated. •  2 types lymphocytes à T cells: controllers of the immune system -trigger a series of immunological reac-ons, mediated by cytokines. •  There are two subclasses of T-helper cells •  Type 1: Th1 •  Type 2: Th2 •  Th1 triggers the protec’ve response to a pathogen such as a virus or bacterium -IgM, IgG, IgA an-bodies are produced •  Th2 is responsible for the IgE-mediated hypersensi’vity reac’on (allergy) -IgE an-bodies are produced

Question 8

Immunological	Process	•  Cytokines	(the	“control	chemicals”	of	the	immune	system)	are	released	•  Each	subclass	produces	a	different	set	of	cytokines	•  The	types	of	cytokines	generated	determine	the	resul-ng	immune	response	ie:	Th2(IL-4,	IL-13)			
																												à	B	cells:		an-body	secre-ng	cells																					memory	cells

Answer 8

g

Question 9

Allergic Response

Answer 9

-Mast cell or ‘allergic cell’ -IgE molecules are bound to surface of the mast cell -uniqueness of the mast cell is __________________ -When an allergen specific with IgE molecules is in contact: -‘degranula-on’ occurs: a series of reac-ons–releasing wide array of molecules ie: histamine, serotonin, (platelet ac-va-ng factor) PAF, leukotrienes, prostaglandins -

Question 10

Pathogenesis

Answer 10

Ingestion of food à “initiatial sensitization” stimulates produc-on of IgE an-bodies à binds to -ssue basophils and mast cells. •  Upon “subsequent ingestion -> binds to specific IgE an-bodies -triggers release of mediators (ie: histamine, or prostaglandins and leukotrienes causing “clinical responseà allergic symptoms)

complex interplay of environmental influence and gene-cs underlying the immunopathogenesis •  microbiome “internal” environmental exposure

Question 11

Risk Factors

Answer 11

Hygiene Hypothesis •  Increased pollu-on -cofactor (not specific) •  Family History •  Time of food introduc-on

Question 12

Prevalenc

Answer 12

Food allergy common in N.A and western countries •  Children (<3yrs. of age) assessed by food challenge: affects 2-10% of popula-on •  5% children: - ⇪ prevalence between 1 ½ - 3 yr. olds 3-4% adults - self repor-ng ⇪ •  18% increase of food allergy prevalence b/w: 1997-2007. •  Israeli children less likely to have peanut allergy vs. Jewish children in UK

Question 13

Symptoms

Answer 13

1. skin and mucous membranes :eczema, hives, itching, swelling of the mouth, face
   2. diges-ve tract
   :abdominal pain/bloating nausea, vomiting diarrhea constipation
   3. respiratory tract
   itchy watery eyes, hay fever, throat tightening
   4. nervous system
   - headache, irritability dizziness, dark circles under eyes
   -
   -
   -

Question 14

Food Allergens

Answer 14

à almost any food can potentially licit an allergic reaction
•  Rela-vely small # of allergens cause a high propor-on of food allergy (Evidence B)
•  Most Common: cow’s milk, soy, wheat, egg, peanut, tree nuts, finned fish, shellfish, sesame Children: < 3 yrs. of age: Cow’s milk, egg, wheat, soy, peanut/treenuts Adults: peanut/treenut, shellfish

Question 15

•  Popula-on of ‘standard risk’ infants or infants with a family history of a 1st degree rela-ve with atopy con-nue to breasqeed while they are introduced to complementary foods, including commonly allergenic foods, at about 6 months of age. •  Importance for food introduc-on to infants in their 6th month -iron content
developementally
immature gi
- - •  “High risk” –infants with severe eczema or egg allergy – rec. to consult a physician/allergist for tes-ng/diagnosis of allergy including food introduc-on

Answer 15

s

Question 16

diagnosis

Answer 16

Diagnosis •  Comprehensive medical history / Physical exam -rule out other medical condi-ons -include symptom diary of adverse reac-ons to foods
•  Skin tests •  Serum specific IgE tes-ng •  Test results alone à not diagnos-c -focus on foods provoking reac-on Evidence B) •  Oral Food Challenge for IgE mediated ( Evidence: A) •  Elimina-on diet; food/symptom diary (Evidence D)

Question 17

Skin Tests

Answer 17

Serum specific IgE skin tests > inflammatory mediators •  Measures of ‘wheal and flare’ •  size of “wheal and flare” reac-on in the skin. •  size measured posi-ve 1 to 3+ •  diameter > 3mm’s + • Foods with higher predic-ve accuracy: egg, fish, tree nuts, milk wheat and peanuts

Question 18

False Posi-ve Tests

Answer 18

-difference is the form which food is applied to the skin compared to immune cells in diges-ve tract •  -skin mast cells by s-muli don’t degranulate the mast cells in the diges-ve tract Ie: raw form in extracted may be degraded during cooking

gastric acid and digestion enzymes can degrade antigens

Question 19

Serum Specific Tests

Answer 19

blood tests indicators of probable sensi-za-on to an allergen Ie: Radioallergosorbent test (RAST) Enzyme-linked Immunosorbent Assay •  sensi-vity broader range than skin tests •  classified in mul-ple classes to increase predic-ve values of test -varied correla-on b/w severity of allergic response and an-bodies in blood •  Clinical hx., level of posi-ve result also influence relevance of test

Question 20

Unproven Tests

Answer 20

IE: Allergen specific IgG measurement

Inaccurate tes-ng, creates false diagnosis, inappropriate guidelines and unbalanced diet plans suggested (Evidence C)

Question 21

Anaphylaxis

Answer 21

Acute, systemic, severe, poten-ally fatal reac-on •  occurs à minutes à up to 2 hrs. •  Any food can trigger anaphylaxis •  Pathophysiology: Mediated by immunoglobulin (IgE) à leads to mast cell and basophil ac-va-on - subsequent quick release of inflammatory mediators ie: histamine, leukotrienes, prostaglandins

Question 22

Pathophysiology of Anaphylaxis

Answer 22

Systemis vasodialation of blood vessels - sudden severe decrease of blood pressure
In the lungs edema of the mucosa and constriction of bronchiiole - obstructing air flow
Second Phase: Biphasic

Question 23

Treatment of Anaphylaxis

Answer 23

Self-Injectable Epinephrine (adrenalin) immediately- 1st line management (Evidence C) •  An-histamines (Benadryl)-block the response of -ssues to histamine •  Transport to hospital •  Hospital: O2 and IV fluids to stabilize •  Other: Steroids (Prednisone), inhaled beta 2 agonists, an-histamines

Question 24

Exercise-Induced Anaphylaxis

Answer 24

Defini/on: •  When a specific food allergen triggers anaphylaxis aCer or during exercise •  Occurs up to 2 hrs. aCer ea-ng •  exerciseà hives, itching, SOB, low blood pressure
Proposed mechanism histamine and other mediators from mast cells •  Exercise triggers the poten-al for release of à •  Factors involved? Ie: Exercise, NSAID’s, weather, stress, menstrual cycle •  Which foods affect? Ie: wheat, celery, shellfish, chicken, peaches, nuts,

Question 25

Nutri-on Assessment

Answer 25

Medical/Family History •  Clinical Data Nutri-on Status •  Diet History -Recommend pa-ent/family keep Food Records -Nutri-on Therapy: Monitoring Symptoms; Evalua-on -In children; monitor growth /development •  Nutri-onal adequacy – preven-on of treatment related nutri-on deficiencies ie: kcals, protein, vitamin D, vitamin E, Calcium, Iron, Zinc) •  Review guidelines: for home, label reading, ea-ng out, friends, during travel •  Discuss preven-on of reac-ons / planning ahead

Question 26

Food Labelling

Answer 26

Educa/on re: Food Labelling: Allergens listed individually: ie: Tree nuts: Almonds, brazil nuts, cashews, hazelnuts, macadamia nuts, pecan, pine nuts, pistachios, walnuts •  New component declara-on •  when an allergen, gluten source or sulphite are 10 ppm or over must be declared on the label -lis-ng the source of allergen in simple terms -in contains statements “not mandatory-” -read labels each -me: ingredient list and in contains statement

1. understand the allergy, how to manage a reac-on 2. monitor foods à home, ea-ng out and travel 3. common foods that contain the allergen 4. read ingredient labels with each use – iden-fy hidden sources of allergens ie: “Brand formats” –differ 5. explain cross-contamina-on / risks 6. precau-onary labelling risks on packaged foods 7. provide nutri-onally appropriate subs-tu-ons 8. plan healthy, allergen-free meals/snacks at hom