Food Allergies and Sensitivities

Question 1

Prevalence of food allergies is based on:

Answer 1

Prevalence of food allergies is based on self-or parental diagnosis, or clinical impressions without complete medical diagnosis.

Question 2

What is the range of food allergies and sensitivies?

Answer 2

• 0.3-7.5% general population
• 4-6% infants
• 1-2% young children
• <1% adults

Question 3

Define: true food allergy

Answer 3

The immunologically mediated adverse reactions resulting from the ingestion of a food or food additive.

Question 4

What are the causes of true food allergy? [4]

Answer 4

1. Heredity (atopic disease)
2. Naturally occurring substances in foods (e.g., mostly proteins)
3. Food additives (e.g., papain enzyme - a component of meat tenderizers)
4. Food contaminants (e.g., penicillin residues

Question 5

What are the mechanisms of true food allergy? [4]

Answer 5

Type 1: Immediate hypersensitivity (involves IgE)
Type 2: Not demonstrated to be associated with food
Type 3: Immune complex responses
Type 4: Delayed hypersensitivity associated with food

Question 6

Define: food allergy.

Answer 6

Immune-mediated inflammatory response to food allergen

Question 7

What are allergens?

Answer 7

• Food proteins to which certain individuals have hypersensitivity reactions
• Glycoproteins that are relatively resistant to digestion and cooking.

Question 8

What are the priority food allergens in Canada?

Identified as foods that cause majority of allergic reactions in Canada

Answer 8

• Peanuts, tree nuts (lectin-reactive glycoproteins)
• Milk & eggs (casein, beta-LG, lactalbulmin)
• Seafood (antigen II; parvalbumin)
• Soy, wheat (beta-conglycinin, glycinin)
• Mustard seed (sin a 1 - an enzyme that is not broken down during digestion or cooking)
• Sulphites (a food additive)

Question 9

More than 90% of IgE-mediated food allergies are caused by:

Answer 9

• Cow’s milk
• Soy
• Hen’s egg
• Peanuts
• Tree nuts (& seeds)
• Wheat
• Fish
• Shellfish

Question 10

What is an IgE-mediated allergic reaction?

Answer 10

A food allergy that is mediated by food-specific immunoglobulin E (IgE) antibodies.

Question 11

What are important mediators in IgE-mediated allergic reaction?

Answer 11

• Histamine
• Prostaglandins
• Leukotrienes

Question 12

What is the first event of IgE-mediated allergic reaction?

Answer 12

Sensitization - once the allergen is consumed, sensitization of the individual results in the production of allergen-specific IgE antibodies.

Question 13

What is the second event of IgE-mediated allergic reaction?

Answer 13

Degranulation and release of chemical mediators - after re-exposure, the allergen crosslinks two IgE antibodies on the surface of mast cell, which results in a change in the membrane and stimulates the release of histamine, heparin, and platelet aggregation.

Question 14

What are the two steps of IgE-mediated allergic reaction?

Answer 14

1. Sensitization
2. Degranulation and release of chemical mediators

Question 15

Describe the mechanism of peanut allergy.

Answer 15

Lectin-reactive glycoproteins - IgE mediated

Question 16

What are the symptoms of IgE-mediated allergies?

Answer 16

• Cutaneous - hives; eczema; dermititis; rash
• Gastrointestinal - nausea; vomiting; diarrhea; cramps
• Respiratory - asthma; wheezing; rhinitis; bronchospasm
• Others - anaphylactic shock; hypotension; swelling of the tongue, larynx; palatal itching

Question 17

Describe acute reactions to IgE-mediated allergic reactions.

Answer 17

• Within 2 hours after ingestion
• Urticaria; angioedema; vomiting

Question 18

What are objective symptoms?

Answer 18

• Any symptom discernable to clinical observers
  
  • Vomiting
  • Urticaria
  • Rash
  • Angioedema
  • Abdominal pain - concerned as the objective endpoint (at least 30 min; intensity to require treatment)
  • Minor criteria used to support:
    
    • Crying
    • Prostration
    • Mood changes
    • Pharyngeal, oral or laryngeal itching
    • Nausea
    • Palor

Question 19

Describe delayed-onset IgE-mediated allergic reactions:

Answer 19

• Within 24-72 hours after food ingestion
• Dermatitis, infantile colic, gastro-esophageal reflux, esophagitis, diarrhea and constipation

Question 20

How are food allergy related reactions avoided?

Answer 20

• Avoid all food and products that contain (e.g. egg and egg) derivatives.
• These include any product whose ingredient list warns it “may contain” or “may contain traces of” egg, peanuts etc.

Question 21

Are allergies outgrown?

Answer 21

• Most children outgrow their allergy by three years of age (e.g. egg).
• However, a severe egg allergy can last a lifetime

Question 22

Are cooked foods allergic?

Answer 22

• Usually not.
• Cooking can alter the protein of a raw egg, but possibly not sufficiently to prevent a reaction.
• For peanuts, allergens are not inactivated.

Question 23

Describe peanut allergy.

Answer 23

• One of the most prevalent allergies
• Symptoms may progress quickly and rapidly progress from mild to severe
  
  • Breathing difficulties
  • Drop in BP
  • Shock
  • Unconsciousness
  • Death

No cure for food allergies!

Completely avoid peanut in diet.

Question 24

Define: NOAEL

Answer 24

No observed adverse effect level - the highest dose that will not produce any adverse effect in that person

Question 25

Define: LOAEL

Answer 25

**Lowest observed adverse effect level** - the lowest dose that produces an adverse effect ## Footnote Range: 0.5 mg up to 8000–10,000 mg of whole peanut (Taylor et al., 2009)

Question 26

Define: population threshold.

Answer 26

The largest amount of peanut that would not cause an adverse reaction in any individual within the total population of peanut-allergic individuals.

Question 27

Discuss: dose distribution.

Answer 27

* Record NOAEL and LOAEL dose for each of 286 subjects during 17 year long study.

Question 28

What is a food sensitivity?

Answer 28

* A.K.A. Food intolerance * Adverse reaction to specific food * **Non-immunological responses** * Anaphylactoid reactions * Metabolic food disorders * Idiosyncratic illnesses

Question 29

What are the types of food sensitivities?

Answer 29

1) Anaphylactoid 2) Metabolic deficiency of enzyme(s) 3) Idiosyncratic

Question 30

What are anaphylactoid reactions?

Answer 30

* A destabilization of mast cell membrane and release of histamine contained therein. Not regarded as a histamine poisoning which occurs when fed ingestion of histamine containing foods) * Resemble anaphylactic reactions but there is no IgE-mediated response * Symptoms mimic those of anaphylaxis: * Polyuria * Respiratory distress * Hypotension * Urticaria * Encephalitis * Fainting * Angioedema * Vomiting * Itching * Unconsciousness * Diarrhea * Abdominal pain * Anxiety

Question 31

What are metabolic reactions?

Answer 31

* Due to inherited defects in the metabolism of a food or food component OR * Due to genetically linked enhanced sensitivity to some food chemical. * Examples: Intestinal β-galactosidase-Lactose intolerance; Erythrocyte glucose-6-phosphate dehydrogenase; Celiac disease - gluten sensitivity results in an immune reaction that causes damage to the surface of small intestine, leading to an inability to absorb certain nutrients.

Question 32

Discuss lactose intolerance.

Answer 32

* Occurrence: 6-12% Caucasians; 60-90% Ethnic groups (Asian, AA, Greek) * Symptoms: vary with intensity; include abdominal cramping, flatulence, diarrhea. * Alternatives * Avoid dairy products, * Lactose-hydrolyzed milk or co-consumption of lactase * Fermented dairy products (e.g. yogurt) * Clinical Diagnosis: Lactose Tolerance Test (LTT) * 50 gm oral dose lactose and measure blood glucose or breath Hydrogen | Metabolic reaction

Question 33

Discuss favism.

Answer 33

* Occurrence: approximately 100 million people worldwide * Mechanism: G6-PDH is needed to reduce GSH and nADPH to prevent oxidative damagae of RBCs. * The Fava or broad bean contain several oxidants (vacine) which damage RBC and causes hemolytic anemia. * Symptoms: vary with intensity; include Pallor, fatigue, dyspnea, nausea, common with hemolytic anemia. * Action: Avoid Fava and Broad beans. | Inherited Glucose-6-phosphate dehydrogenase deficiency in red blood cell

Question 34

Describe idiosyncratic reactions.

Answer 34

* These reactions show a link between ingestion of foods and illness without any defined mechanism. * Examples: sensitivity to sulfite, tartrazine, monosodium glutamate, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT).

Question 35

Discuss sulfite sensitivity.

Answer 35

* Sensitivity may be due to a partial deficiency of the enzyme sulfite oxidase * The most common reaction with exposure to sulfites is similar to asthma-like symptoms | Idiosyncratic reaction

Question 36

Discuss sulfite-induced asthma.

Answer 36

* Must declare sulfites on food label if in excess of 10 ppm TSO2 * Widely used to prevent enzymatic and non-enzymatic browning, antimicrobial agent and provide antioxidant protection as well as a bleaching agent in processing fruits * Level in foods will vary from * Lowest concentration: <10-100 ppm-shrimp, juice * Medium concentration: 100-300 ppm-wine, molssases * Highest concentration: 500-2,500 ppm-dried fruits.

Question 37

What are treatments for sulfite induced asthma?

Answer 37

**Specific avoidance diet** - Read labels - Knowledge of possible hidden allergens **Pharmacological** - Antihistamines - Epinephrine, Adrenaline - Cortisone

Question 38

Discuss a partial list of food related idiosyncratic reactions. ## Footnote Proven and unproven

Answer 38