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Lecture - Food Allergies - Food Allergy Adverse Reactions...

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Food “Allergy” Adverse Reactions to Food 30% of population report family member with food “allergy” Actual % estimates vary <1-7% Subpopulations/ethnic groups differ markedly Most Common Allergic Foods/Groups Cows milk • Crustacea • Eggs • Fish • Peanuts • Soybean Tree nut • Wheat
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Adverse Food Reactions Food Allergy Food Sensitivity Food Intolerance General terms that can be applied to any clinically abnormal response to food or food additives. Many symptoms are similar Types of Adverse Food Reactions • Allergy • Non-immune anaphylaxis (anaphylactoid) • Intolerance • Metabolic • Idiosyncrasy • Pharmacological • Toxicity Types of Food Sensitivities and Allergies True food allergy Food Sensitivities – Anaphylactoid reactions – Metabolic Food Disorders – Idiosyncratic Reactions Some in several classes
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Food Allergy Hypersensitivity Immune-mediated reaction Can be triggered by very small amounts of food Occurs on second exposure or to a cross reacting antigen Anaphylaxis and cutaneous reactions most common Food Allergies History Observed since early Greeks and Romans Injected normal person with fish extract - no effect (1921) Injected serum of sensitive person, then fish extract - allergic reaction 1966 discovered IgE in serum was cause Food Allergy Production of IgE antibodies IgE bind to surface of mast cells or basophils Second exposure to allergen Allergen crosslinks IgE on surface Release of histamine, bradykinin Allergic reaction
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Food Allergy Symptoms Respiratory = asthma, wheezing, bronchiospasms, dyspnea Cutaneous = urticaria (hives), eczema, rash, pruritis Gastrointestinal = vomiting, diarrhea, abdominal pain Inflammation, vasoconstriction, hypotension, chest pain , nausea
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Food Allergy Symptoms (cont) Other = anaphylactic shock Mild and annoying to fatal Depend on amount ingested and length of time from initial exposure Not all symptoms in all people Food Allergy Small subpopulation at risk <1% 65% of susceptible people have close relative with allergy Increased intestinal permeability to macromolecules predisposes – viral gastrointeritis, premature birth, cystic fibrosis Exercise-Induced Anaphylaxis (EIA) Exercise preceded or followed by specific foods – shellfish, peaches, celery, wheat Mechanism unknown - increased responsiveness of mast cells
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Diagnosis of Food Allergy Self/parental often erroneous Food diary-when/what/how much Double-blind food challenge(DBFC) – neither patient nor doctor know if placebo or allergen (crossover) Skin prick test • RAST Skin Prick Test To determine if IgE involved Usually preliminary test Apply allergen extract to skin Scratch to increase access to blood Inflammation results from release of histamine, edema and swelling Positive control = histamine
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