First Aid, Chapter 7 Hypersensitivity Disorders, Food Allergy Flashcards
On a vacation in Florida, a 39-year-old man orders mahi mahi in a restaurant and, within 20 minutes of eating it, develops abdominal cramps, vomiting, swelling of the tongue, and trouble breathing. He has eaten fish all of his life. Skin testing to all white fish is negative. What is the cause of this patient’s illness?
Scombroid fish poisoning
What are categories of nonimmune-mediated adverse food reactions? What are examples of each of them?
-Metabolic: Lactose intolerance, galactosemia, alcohol intolerance
-Pharmacologic: Caffeine (makes you jittery), tyramine in aged cheeses (headaches and migraines), Scombroid fish poisoning (releases histamine-like chemicals)
-Toxins (not host-specific): Food poisoning
-Psychologic: Food aversion, anorexia nervosa
Other: Auriculotemporal syndrome (vasodilatation), gustatory rhinitis (runny nose from spicy or hot foods), Frey’s syndrome (transient, unilateral and bilateral facial flushing or sweating after ingestion of spicy or flavored foods; due to damage to auriculotemporal nerve)
What mechanism are most non-IgE mediated food allergy reactions?
T-cell mediated mechanisms. Typically, these reactions are not immediate and involve primarily the gastrointestinal system.
What are the typical IgE-mediated food allergy symptoms? What are mixed IgE and Non-IgE food disorders? What are Non-IgE mediated food reactions?
IgE-mediated: urticaria, angioedema, asthma, rhinitis, GI anaphylaxis, Oral allergy
Mixed IgE and cell mediated: Atopic dermatitis, eosinophilic disorders
Non-IgE (cell) mediated: dermatitis herpetiformis, Heiner’s syndrome, enterocolitis, enteropathy, proctocolitis, celiac
What is the prevalence of food allergy in children? adults?
6% of young children and 3–4% of adults have food allergies
What percentage of food reactions are fruits and vegetables? Are they severe?
Reactions to fruits and vegetables are approximately 5%, but usually are not severe.
What is the prevalence of soy allergy in children? wheat allergy in children?
0.4% each
What is the most common trigger of fatal anaphylaxis in North America?
peanut
What is the prevalence of each of the following in children and adults:
milk, egg, peanut, tree nuts, fish, shellfish, overall
Children (%) Adults (%) Milk 2.5 0.3 Egg 1.3 0.2 Peanut 0.8 0.6 Tree nuts 0.2 0.5 Fish 0.1 0.4 Shellfish 0.1 2.0 Overall 6 3.7
What are class 1 allergens? How does the breach in tolerance occur?
Primarily from food that is ingested (i.e., GI sensitization). Such a breach in oral tolerance typically occurs when food proteins stable to digestion are encountered by sensitive individuals. Class I allergens such as egg or peanut may invade through the skin.
What are characteristics of type 1 allergens? What is their size? Are they heat stable? Water insoluble or soluble? What are examples?
- 10–70 kD glycoproteins; heat resistant, acid stable, and water soluble
- Examples include cow’s milk protein (casein and whey), egg (ovalbumin and ovomucoid), peanut (vicilin, conglutin, and glycinin), fish (parvalbumin), and shellfish (tropomyosin)
- This class of allergens also includes nonspecific lipid-transfer proteins in apple and corn.
What type of epitope yields a more prolonged food allergy vs. a more transient mild allergy?
Linear epitope = more prolonged allergy, allergen is “stable” and persistent Conformational epitope = mild, transient allergy.
What are class 2 allergys? How are they formed? How does this cause food allergy? What are characteristics of type 2 allergens?
Formed primarily from respiratory sensitization. Sensitization to labile proteins encountered via the respiratory route, such as pollens, results in IgE antibodies that recognize homologous epitopes on food proteins from plants.
-Some patients exhibit symptoms of pruritus limited to the oral mucosa when eating fresh fruits and vegetables, termed pollenfood allergy syndrome.
Type 2 allergens are characterized by the following:
-Plant-derived and labile
-Predominantly in superfamilies of cupin and prolamin, and the protein families of the plant defense system
What factors increase the risk of fatal food anaphylaxis?
Factors associated with increased risk for fatal reaction include delayed epinephrine administration, young adult or teen, underlying asthma, and absence of skin symptoms.
What particular foods are associated with food-associated exercise-induced anaphylaxis?
Often associated with particular foods such as celery and wheat (omega-5 gliadin) in the context of physical activity.
How does sensitization of pollens result in food allergy in pollen-food allergy syndrome? What proteins are involved? Is it IgE mediated? Do symptoms vary within an individual?
Sensitization to allergens such as Bet v 1 (birch) through the respiratory route may result in cross-reactivity to type 2 allergens such as Mal d 1 (apple, peach), and present with oral pruritus when eating fresh fruit. This is IgE-mediated. Symptoms may vary by season.
What are the Bet v 1 homologues in fruit? In what forms of food does this protein cause reactions?
PR-10: Bet v 1 homologues in the pulp of the fruit; sensitive to heat, therefore, no reaction to cooked/processed fruit; symptoms usually restricted to the mouth.
What proteins are located in the peel of fruits? What are their heat/digestion properties? What type of reaction do they cause?
Nonspecific lipid transfer proteins: Located primarily in the peel; stable to heat and digestion, therefore reacts to cooked/processed fruit as well; reaction may be more severe
What are the Bet v 2 homologues in fruit? In what forms of food does this protein cause reactions?
Profilin: Bet v 2 homologues, sensitive to heat, therefore, no reaction to cooked/processed fruit; symptoms usually restricted to the mouth
What proteins are located in the stones of fruit? How stable are they? In what forms of food does this protein cause reactions?
Storage proteins: Located in the fruit stone (seed/nut/kernel); stable to heat and proteases, therefore, react to cooked/processed foods
What types of food are cross-reacting carbohydrate determinants found in? What types of reactions do they cause? What are some examples?
Found in plants and invertebrates (not mammals); may cause no reaction, or anaphylaxis; examples include latex, bee/wasp, cockroach, mite, and shellfish
What are the symptoms in Heiner’s syndrome? How is it diagnosed? What is the treatment?
Sx: Recurrent pneumonia, pulmonary infiltrates, hemosiderosis, iron deficiency anemia, and FTT
Diagnosis: Hx, peripheral eosinophilia, milk precipitins, lung biopsy
Tx: elimination diet
What is the mechanism of Dermatitis herpetiformis? What are the symptoms? What is the distribution? What disease is it associated with? How is it diagnosed?
Mechanism: cell-mediated
Symptoms: Itching, papulovesicular rash over extensor surfaces and buttocks (acral distribution) on sun-exposed areas of arms and legs; associated with celiac disease (gluten sensitive)
Diagnosis: Skin biopsy (IgA deposition), celiac disease antibodies: IgA antigliadin and antitransglutaminase antibodies, and endoscopy
What is the mechanism of eosinophilic gastroenteritis? What are the symptoms? How is it diagnosed?
Mechanism: IgE mediated and/or cell-mediated
Symptoms: Recurrent abdominal pain, vomiting, early satiety, FTT, and peripheral eosinophilia
Diagnosis: Hx, SPTs endoscopy or biopsy and elimination diet
What is the mechanism of food protein induced proctocolitis? What are the symptoms? How is it diagnosed?
Mechanism: cell-mediated
Symptoms: Blood in stool, first few months of life, and no FTT
Diagnosis: SPTs, elimination diet, challenge results in sx in 72 hr
What is the mechanism of food protein induced enterocolitis? What are the symptoms? How is it diagnosed?
Mechanism: Cell-mediated
Symptoms: Vomiting and diarrhea, +/- blood, FTT, vomiting one to three hours after eating, and hypotension
Diagnosis: SPTs, elimination diet, challenge results in sx in 1– 2 hr
What is the mechanism of food protein induced enteropathy/celiac disease? What are the symptoms? How is it diagnosed?
Mechanism: cell-mediated
Symptoms: Diarrhea, steatorrhea, abdominal distension, flatulence, oral ulcers, and weight loss
Diagnosis: Endoscopy and biopsy, IgA, celiac abs, and elimination diet
When can celiac disease antibodies be falsely negative?
If IgA is absent, serology for celiac disease can be falsely negative. Antibodies often positive in patients with celiac disease include IgAantigliadin antibodies and tissue transglutaminase antibodies
What are the symptoms of galactose-a-1,2-glasctose allergy? What foods is it found in? What may be in the patient’s history? What type of allergen is this? What drug can it be found in?
urticaria, angioedema, or anaphylaxis 3–6 hours after ingesting beef, lamb, or pork. May have a history of a tick bite. Unlike common allergens, which are usually proteins, this allergen is a carbohydrate found as part of the glycoproteins, including the chemotherapeutic monoclonal antibody cetuximab.
What percentage of patients with negative serum IgE to foods have a reaction?
10-25%
What component-IgE tests can be useful in peanut allergy to predict the reaction?
Component-resolved diagnostics can identify IgE specific for conformational epitopes, or specific epitopes that may help predict whether a reaction may be systemic (i.e., Ara h 2) or oral (i.e., Ara h 8) in individuals with peanut allergy.
What percentage of children who outgrow peanut and tree nut allergy will redevelop it if they avoid it?
7-9%
When do infants with non-IgE associated GI allergies outgrow the allergy?
Infants outgrow it by age 1-3 years.
When do toddlers and adults outgrow non-IgE associated GI allergies?
They are more persistent than in infants.
Does eating baked milk/egg expedite the resolution of IgE mediated allergy to nonbaked milk/egg?
yes
What role does exclusive breast feeding for the first 4 months play in risk of AD and food allergy?
Exclusive breast feeding for the first 4 months of life may decrease the risk of AD and cow’s milk protein allergy in the first 2 years of life.
What might avoidance of solid foods in the first 4 months of life decrease the risk of?
AD
What role might vitamin D, antioxidants, fats, and antacids play in food allergy?
Vitamin D, antioxidants, fats; antacids may play a role in exposure to intact proteins.
