Food Allergies
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Not as common as you might think
First, some definitions
• Antigen-a compound (usually protein) that in and of itself can produce an immune response
– Bacteria, viruses
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Hapten-a compound that will produce an immune response once it binds to human protein
– Certain chemicals, nickel
What is an allergy?
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An abnormal immune response to a substance that most other people find harmless
– Protein in cat saliva, pollen, dust mite feces
– Foods--peanuts, tree nuts, milk, eggs, corn, shrimp
How common are food allergies?
0.5-3.8% of young children
0.1-1.0% of adults
What happens during a food allergy “attack”?
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Your body has antibodies (specifically IgE type) against the allergen
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When you ingest the offending food, the allergen binds to the IgE
• The IgE-allergen complex binds to a type of white blood cells called mast cells
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The mast cells then secrete a substance called histamine
What does histamine do?
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Vasodilation (blood vessels get larger in diameter)
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Capillaries become more permeable
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Fluid leaks out
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In lungs, histamine causes bronchospasm (asthma)
Anaphylactic Shock
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Most severe and potentially deadly manifestation of allergies
• Bronchospasm, difficulty breathing, low blood pressure, swelling of bronchial passages
• People prone to these severe reactions should carry an EpiPen with them at all times

Signs & Symptoms of Food Allergy
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Gastrointestinal distress-vomiting, diarrhea
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Children-failure to thrive due to gut symptoms
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Skin rashes, itching
• Respiratory symptoms are less common, but can occur
Diagnosis of Food Allergy
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Skin tests
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RAST test--a blood test
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Concurrent food and symptom diary
• Elimination of suspect food
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Double-blind, placebo-controlled food challenge
• Easier said than done!
Management of Food Allergies:
“Just don’t eat it”
How come?
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“Modified food starch” can be wheat or corn
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Dry milk or whey, dried egg, and soy can be sneaked into many foods
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Peanut residues may appear in non-peanut-containing candy
The Food Allergy and Anaphylaxis Network
• www.foodallergy.org
Celiac Disease
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A unique type of food allergy
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An allergy to gliadin (component of wheat, rye, barley, and triticale)
Celiac Disease
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Incidence 1 in 250
• Reaction against small peptides in gliadin that are high in the amino acids glutamine and proline
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Cannot be detected by RAST test, since IgA is predominant antibody produced

Celiac disease is often undiagnosed for years
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Villi in small intestine become blunted
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Result in malabsorption of all nutrients
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Some people develop bone or skin problems
• Definitive diagnosis-intestinal biopsy and blood test for anti-gliadin antibodies
Treatment of Celiac Disease
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Lifelong avoidance of foods containing wheat, rye, barley, triticale
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Another easier said than done concept
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Celiacs may also be lactose intolerant until villi recover after gliadin abstinence
Another good source of info
• The Celiac Disease Foundation
• www.celiac.org
Food Intolerance
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A non-immune adverse reaction to a food
Food intolerance examples
• MSG
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Sulfites--more common in asthma patients
• Lactose intolerance
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Fructose intolerance