Transcript Food Allergies - Iowa State University

FOOD ALLERGIES
WHAT IS A FOOD ALLERGY?
An immune reaction that occurs after eating a
certain food
 Also known as a food hypersensitivity
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Autoimmune disease
Elicits an abnormal immune response to a harmless food
substance
 Antibodies are released to fight the allergen
 Allergen is usually a protein
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CLASSIFICATION OF ALLERGIES
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Allergic reactions are classified into non-IgEmediated, IgE-mediated or mixed response
Non-IgE
 Slower in onset, primarily gastrointestinal reactions
 IgE mediated
 Causes histamine and other chemicals to be released
which trigger allergy symptoms
 Rapid in onset, symptoms include anaphylaxis &
urticaria
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SYMPTOMS
Allergy symptoms can occur seconds to hours
after ingestion of the allergen
 Most common symptoms:
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swelling, sneezing, nausea, GI distress
Skin
• Swelling of lips,
tongue & face
• Itchy eyes
• Hives
• Rash
Respiratory Tract
• Itching or
tightness of throat
• Shortness of
breath
• Dry or raspy cough
• Runny nose
• wheezing
Gastrointestinal
Tract
• Abdominal pain
• Nausea
• Vomiting
• diarrhea
FOODS MOST COMMONLY
ASSOCIATED WITH ALLERGIC
REACTIONS
FREQUENTLY ALLERGENIC FOODS
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Most common food
allergies in young
children:
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Milk (casein, whey)
Eggs
Wheat (gluten)
Soy
Peanuts
Tree nuts
Shellfish
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Most common food
allergies in older
children & adults
Fish
 Shellfish
 Peanuts
 Tree nuts
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FOOD ALLERGY VS FOOD INTOLERANCE
Reactions to food consist of a
variety of reactions to food or
food additive ingestion
 Usually not allergenic and
caused by food intolerance
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Symptom-inducing food
properties
 Metabolic disorders
 Bacterial food contamination
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VARIABILITY IN PREVALENCE
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Determination of the exact
prevalence
is difficult
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Considerable variation in data
collection
Self-reporting,
physician assessment,
skin tests, IgE levels
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However, self-reports indicate
that food allergy incidences
are on the rise
 Food allergy in infants are
most common
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INCREASED EXPOSURE
Development of an allergy depends
on the structure of the protein, dose
of the antigen and the genetic
susceptibility of the host
 Non-oral exposure may be a primary
risk factor
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Damaged skin may allow increased
exposure before tolerance has been
developed through oral ingestion
FOOD ALLERGIES
PEANUT
Milk
 Egg
 Tree Nuts
 Fish
 Shellfish
 Wheat
 Soy
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PEANUT ALLERGY
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Peanut sensitization does not conclude an allergy
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About 95% of sensitized individuals are not clinically
allergic
Attracted the most attention because it is
relatively common, typically permanent and
often severe
 Significantly increased globally in the past
decade
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2-3x as common
PEANUT ALLERGY
HYGIENE HYPOTHESIS
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Antibiotic treatment increased ease of peanut
sensitization
Studies from many countries show that early
exposure of viral infection may produce a
proactive effect
Children born into families with several siblings
tend to have a reduced frequency of allergic
sensitization
PEANUT ALLERGY
PROCESSING
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Allergenic protein content depends on
processing and varies by brand
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Higher allergenic protein content:
More mature, larger kernels
 Drying or curing at higher temperatures
 Roasting
 Whipped or emulsified peanut butter
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Less allergenic protein content:
Small kernels
 Raw peanuts
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Highly processed oils had no detectable
protein
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It is generally advised that peanut-allergic
patients avoid all peanut oils
PEANUT ALLERGY
AGE OF INTRODUCTION
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Sensitization to peanuts
typically occurs at an early
age, therefore such patients
are more likely to react at
first exposure
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No conclusive evidence has
been found to support the
theory that the allergy is
developed in utero
Food allergy manifests most
commonly in infancy,
peaking at 1 year of age and
declining by age 3
 Recommendations only in
place for at-risk infants
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MILK ALLERGY
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2.5% of children younger than 3
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Develops in first year of life
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Most children will outgrow it
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Baby Formula
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Hidden Sources: deli meats, non dairy items,
canned tuna fish, restaurant foods and sauces
EGG ALLERGY
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Affect approximately 1.5% of young children
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Likely to be outgrown
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Most allergic reactions associated with egg
involve the skin
Hidden sources: coffee drinks with foam topping,
soft or hard pretzels, cooked pasta, egg
substitutes.
Vaccines
TREE NUT ALLERGY
1.8 million Americans
 Allergic are among the leading causes of fatal
and near-fatal reactions to foods
 Tree nuts = walnuts, almond, hazelnuts,
coconuts, cashews, pistachios, and Brazil nuts
 Tend to have a lifelong allergy
 Hidden sources: Salads and salad dressing,
barbecue sauce, breading for chicken, pancakes,
meat-free burgers, pasta, honey, fish dishes, pie
crust, mandelonas (peanuts soaked in almond
flavoring), mortadella (may contain pistachios)
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FISH AND SHELLFISH ALLERGY
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2.3% of Americans
Salmon, tuna, and halibut
Avoid all varieties
Lifelong
Avoid seafood restaurants
Asian restaurants-fish sauce
Read ingredient lists
Avoid areas where fish is being handled or cooked
Hidden Sources: Salad dressing, Worcestershire
sauce, bouillabaisse, imitation fish or shellfish,
meatloaf, barbecue sauce (some are made from
Worcestershire)
WHEAT ALLERGY
Common in children
 Often confused with celiac disease
 IgE-mediated response to wheat protein
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May tolerate other grains
Symptoms range from mild to severe
Sources: baked goods (wheat flour), pasta, sauces
thickened with flour, cereals, crackers
Substitute with amaranth, barley, corn, oat,
quinoa, rice, rye, tapioca
SOY ALLERGY
More common food allergies in babies and
children
 Major ingredient in food products
 Hard to avoid
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Dietitian should be consulted
Symptoms typically mild
Hidden sources: baked goods, canned tuna,
cereals, crackers, infant formulas, peanut butter,
sauces, and soups.
 Typically can tolerate soybean oil
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CAN SOME INDIVIDUALS BE ALLERGYPRONE?
Patients reacting to greater numbers of
allergenic epitopes experienced more severe
allergic reactions & to smaller doses
 Children with egg &/or milk allergies more
susceptible
 Peanut-allergic patients do not usually react to
other legumes such as green beans, lima beans,
navy beans
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95% of peanut-allergic patients can tolerate soy
TREATMENT OPTIONS
CURING FOOD ALLERGIES
There is currently no cure for food allergies
 The current recommendation is to avoid the
allergen
 Promising treatments on the way
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IMMUNOTHERAPY
Sublingual immunotherapy (SLIT)
 Oral Immunotherapy (OIT)
 Contact of an antigen induces tolerance
 Patient is given increasing amounts of the
allergen
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Conclusion: may be effective during therapy (for
egg, milk and hazelnut) but there is no evidence
for long-term tolerance
ANTI-IGE THERAPY
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TNX-901 was given in varying doses
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450 mg dose significantly increased threshold of
reactivity to peanuts from 178 mg (about ½ a peanut)
to 2.8 g (about 9 peanuts)
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Enough to protect against accidental ingestions
Results were inconsistent
Would require bimonthly or monthly injections
for rest of patients’ life
Conclusion: May be of use in severe cases
ENGINEERED RECOMBINANT PROTEIN
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The three major allergenic proteins in peanut
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Ara h 1, 2 & 3 were isolated
Necessary for binding with IgE
 The recombinant proteins were significantly
more effective at blocking symptoms
 The modified Ara h 1, 2 & 3 proteins have been
manufactured and are undergoing testing before
application for FDA approval
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CHINESE HERBAL MEDICINE
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A 9-Herb preparation termed Food Allergy
Herbal Formula (FAHF)-2 blocks anaphylactic
symptoms
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Provided full protection against symptoms in a
clinical study performed on mice
The FDA has recently approved a botanical
Investigational New Drug application
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A phase-I clinical trial will soon be underway
SUMMARY COMMENTS
Food allergy is an autoimmune response often
mistaken for food intolerance
 Peanut allergy appears to be increasing
 Genetic, environmental and immunological
influences
 Recent studies have led to improved diagnoses,
management and patient education
 Numerous approaches to treatment are
underway
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