Food Allergy Module 2 Flashcards
9 top food allergens
Peanuts
Tree nuts
Eggs
Fish
Shellfish
Soy
Wheat
Dairy
Sesame (new)
symptoms of food allergy
Itching or swelling in your mouth
Vomiting, diarrhea, or abdominal cramps and pain
Hives or eczema
Tightening of the throat and trouble breathing
Drop in blood pressure
NIAID definition
An adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.
immune-mediated reaction to food what cells are involved
IgE (antibodies)
Non-IgE (immune cells)
Eosinophils
T cells
Mast cells
Mixed (antibodies and cells)
Should not be confused with INTOLERANCE (unknown or other mechanism)
allergies must be __ with repeat exposure
allergies must be reproducible with repeat exposure
allergens are __ or __ and are generally __ and __
allergens are proteins or glycoproteins and are generally heat resistant and acid stable
major allergenic foods account for >__% of food allergy
includes __ and __
major allergenic foods account for >90% of food allergy
includes egg whites and tree nuts also top 9!
allergies most common in children:
__% outgrow by __ years
allergies most common in children: milk, egg, soy, and wheat
50% outgrow by 5-7 years
allergies that persist into adulthood:
__% outgrow
allergies that persist into adulthood: peanut, tree nuts, finned fish, shellfish
20% outgrow peanut, 1% outgrow tree nuts
2 treenut cross-reactivities
Cashew and pistachio
Pecan and walnuts
cross-sensitization
cross-reactivity
cross contamination
cross-sensitization: have antibodies
cross-reactivity: sensitivty to both cow’s milk and goat’s milk
cross contamination: kitchen issue
peanuts are cross-reactive with
other legumes: peas, lentils, beans
oral allergy syndrome most common in
adults, but seen in kids
clinical features of OAS
rapid onset oral pruritus
rarely progressive
epidemiology of OAS
prior sensitization to pollens
key foods in OAS
RAW fruits and vegetables
cause of OAS
cross reactive proteins in pollen and food
how does OAS work only with raw things?
allergens are heat sensitive, cooked versions are usually okay
birch cross reactivity
Apple, carrot, celery, cherry, pear, hazelnut
ragweed cross reactivity
Banana, cucumber, melons
grass cross reactivity
Melon, tomato, orange
mugwort cross reactivity
Melon, apple, peach, cherry
clinical history consistent with food allergy
Immediate onset
Specific symptoms as above
No history of tolerating consistent prior ingestion
Common food allergens are COMMON
clinical history NOT consistent with food allergy
Delayed onset
Symptoms NOT as above
GI (more lower than upper), neurologic, behavioral, vague rashes
Recurring hives
Chronic asthma or nasal allergy symptoms Occurring inconsistently
History of tolerating consistent prior ingestion
Has ingested numerous times previously
Not a common food allergen (strawberries, kiwi, tomatoes)
recommended tests for allergies
Skin prick test
ImmunoCAP-RAST Serum IgE testing
Elimination diet: strict, 2-6 weeks, must reintroduce if no change
GOLD STANDARD = oral food challenge
NOT recommended tests for allergies
Patch tests
Intradermal tests
Unproven tests (IgG, kinesiology, VEGA, NAET, ALCAT, etc.)
ImmunoCAP-RAST testing steps
- patient’s serum with IgE is added
- enzyme-labeled antibodies added
- developing agent is added
- fluorescence is measured
positive ImmunoCAP-RAST test means
sensitization
ImmunoCAP-RAST test
- Many false positives BAD screening test >50% of people test + for foods they are not reactive to (more common in older children and adults)
- Moderate sensitivity and specificity (“accuracy”)
Sensitivity and specificity varies by food - Higher levels are more associated with clinically relevant “positive” tests
- Good negative predictive value
Be careful of non-IgE food allergy
= NOT equivalent to a diagnosis of allergy
USE clinical HISTORY to interpret (aka “pre-test probability”)
positive IgE and no symptoms =
sensitivty
sensitivity process
Eat peanuts
Dendritic cells present peanut particles to peanut specific T cells
Th2 cells stimulate B cells to make antibodies specific for peanuts
Peanut specific IgE antibodies bind mast cells and go to recognize peanut, nothing happens
positive IgE and symptoms
allergy
allergy process
IgE on allergy mast cells binds peanut protein, releases histamines, causes symptoms
management and treatment of allergies
- strict dietary avoidance
- management of acute allergic reactions: epinephrine, benadryl, zyrtec
- oral food challenges
- immunotherapy
avoidance
- STRICT avoidance
- label reading
- precautionary allergy labeling (PALs)
may contain, same facility
treating anaphylaxis: epinephrine
dose
0.01 mg/kg (max 0.5 mg)
treating anaphylaxis: epinephrine
route
intramuscular
Higher and quicker peak serum levels compared to subcutaneous
treating anaphylaxis: epinephrine
location
anterior, lateral thigh (vastus lateralis)
Higher and quicker peak serum levels compared to deltoid
treating anaphylaxis: epinephrine
frequency
~5-15 minutes (adjusted clinically)
treating anaphylaxis: adjunct treatments
Antihistamine (H1 and H2 Blockers) NOT FIRST-LINE THERAPY
Slow onset (e.g. 30 minutes)
Helpful for urticaria, angioedema, pruritus
Little effect on blood pressure
Addition of H2 blockade (may improve treatment of cutaneous manifestations)
WILL NOT STOP ANAPHYLAXIS
Adrenergic agents
Inhaled beta-2 agonists may be useful for bronchospasm refractory to epinephrine
Corticosteroids NOT FIRST-LINE THERAPY
May prevent protracted/biphasic course but not proven
treating anaphylaxis: adjunct/advanced treatment options
Oxygen
Fluid resuscitation
Vasopressors
Glucagon
*Presumptive for epinephrine recalcitrant/beta-blockade
Physical position during anaphylactic shock (unless precluded by vomiting or respiratory distress)
*Recumbent with legs raised
*Case reports of death when raised to upright position (“empty ventricle”)
reaction does not indicate
allergy
what is the main way to diagnose IgE-mediated allergies
clinical history
pathogenesis of food allergy is
still unknown
