First Aid, Chapter 7 Hypersensitivity Disorders, Food Allergy

Question 1

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?

Answer 1

Scombroid fish poisoning

Question 2

What are categories of nonimmune-mediated adverse food reactions? What are examples of each of them?

Answer 2

-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)

Question 3

What mechanism are most non-IgE mediated food allergy reactions?

Answer 3

T-cell mediated mechanisms. Typically, these reactions are not immediate and involve primarily the gastrointestinal system.

Question 4

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?

Answer 4

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

Question 5

What is the prevalence of food allergy in children? adults?

Answer 5

6% of young children and 3–4% of adults have food allergies

Question 6

What percentage of food reactions are fruits and vegetables? Are they severe?

Answer 6

Reactions to fruits and vegetables are approximately 5%, but usually are not severe.

Question 7

What is the prevalence of soy allergy in children? wheat allergy in children?

Answer 7

0.4% each

Question 8

What is the most common trigger of fatal anaphylaxis in North America?

Answer 8

peanut

Question 9

What is the prevalence of each of the following in children and adults:
milk, egg, peanut, tree nuts, fish, shellfish, overall

Answer 9

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

Question 10

What are class 1 allergens? How does the breach in tolerance occur?

Answer 10

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.

Question 11

What are characteristics of type 1 allergens? What is their size? Are they heat stable? Water insoluble or soluble? What are examples?

Answer 11

• 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.

Question 12

What type of epitope yields a more prolonged food allergy vs. a more transient mild allergy?

Answer 12

Linear epitope = more prolonged allergy, allergen is “stable” and persistent Conformational epitope = mild, transient allergy.

Question 13

What are class 2 allergys? How are they formed? How does this cause food allergy? What are characteristics of type 2 allergens?

Answer 13

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

Question 14

What factors increase the risk of fatal food anaphylaxis?

Answer 14

Factors associated with increased risk for fatal reaction include delayed epinephrine administration, young adult or teen, underlying asthma, and absence of skin symptoms.

Question 15

What particular foods are associated with food-associated exercise-induced anaphylaxis?

Answer 15

Often associated with particular foods such as celery and wheat (omega-5 gliadin) in the context of physical activity.

Question 16

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?

Answer 16

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.

Question 17

What are the Bet v 1 homologues in fruit? In what forms of food does this protein cause reactions?

Answer 17

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.

Question 18

What proteins are located in the peel of fruits? What are their heat/digestion properties? What type of reaction do they cause?

Answer 18

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

Question 19

What are the Bet v 2 homologues in fruit? In what forms of food does this protein cause reactions?

Answer 19

Profilin: Bet v 2 homologues, sensitive to heat, therefore, no reaction to cooked/processed fruit; symptoms usually restricted to the mouth

Question 20

What proteins are located in the stones of fruit? How stable are they? In what forms of food does this protein cause reactions?

Answer 20

Storage proteins: Located in the fruit stone (seed/nut/kernel); stable to heat and proteases, therefore, react to cooked/processed foods

Question 21

What types of food are cross-reacting carbohydrate determinants found in? What types of reactions do they cause? What are some examples?

Answer 21

Found in plants and invertebrates (not mammals); may cause no reaction, or anaphylaxis; examples include latex, bee/wasp, cockroach, mite, and shellfish

Question 22

What are the symptoms in Heiner’s syndrome? How is it diagnosed? What is the treatment?

Answer 22

Sx: Recurrent pneumonia, pulmonary infiltrates, hemosiderosis, iron deficiency anemia, and FTT

Diagnosis: Hx, peripheral eosinophilia, milk precipitins, lung biopsy

Tx: elimination diet

Question 23

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?

Answer 23

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

Question 24

What is the mechanism of eosinophilic gastroenteritis? What are the symptoms? How is it diagnosed?

Answer 24

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

Question 25

What is the mechanism of food protein induced proctocolitis? What are the symptoms? How is it diagnosed?

Answer 25

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

Question 26

What is the mechanism of food protein induced enterocolitis? What are the symptoms? How is it diagnosed?

Answer 26

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

Question 27

What is the mechanism of food protein induced enteropathy/celiac disease? What are the symptoms? How is it diagnosed?

Answer 27

Mechanism: cell-mediated

Symptoms: Diarrhea, steatorrhea, abdominal distension, flatulence, oral ulcers, and weight loss

Diagnosis: Endoscopy and biopsy, IgA, celiac abs, and elimination diet

Question 28

When can celiac disease antibodies be falsely negative?

Answer 28

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

Question 29

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?

Answer 29

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.

Question 30

What percentage of patients with negative serum IgE to foods have a reaction?

Answer 30

10-25%

Question 31

What component-IgE tests can be useful in peanut allergy to predict the reaction?

Answer 31

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.

Question 32

What percentage of children who outgrow peanut and tree nut allergy will redevelop it if they avoid it?

Answer 32

7-9%

Question 33

When do infants with non-IgE associated GI allergies outgrow the allergy?

Answer 33

Infants outgrow it by age 1-3 years.

Question 34

When do toddlers and adults outgrow non-IgE associated GI allergies?

Answer 34

They are more persistent than in infants.

Question 35

Does eating baked milk/egg expedite the resolution of IgE mediated allergy to nonbaked milk/egg?

Answer 35

yes

Question 36

What role does exclusive breast feeding for the first 4 months play in risk of AD and food allergy?

Answer 36

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.

Question 37

What might avoidance of solid foods in the first 4 months of life decrease the risk of?

Answer 37

AD

Question 38

What role might vitamin D, antioxidants, fats, and antacids play in food allergy?

Answer 38

Vitamin D, antioxidants, fats; antacids may play a role in exposure to intact proteins.