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FOOD 525 > Food Allergies and Sensitivities > Flashcards

Food Allergies and Sensitivities Flashcards

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1
Q

Prevalence of food allergies is based on:

A

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

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2
Q

What is the range of food allergies and sensitivies?

A
  • 0.3-7.5% general population
  • 4-6% infants
  • 1-2% young children
  • <1% adults
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3
Q

Define: true food allergy

A

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

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4
Q

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

A
  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
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5
Q

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

A

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

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6
Q

Define: food allergy.

A

Immune-mediated inflammatory response to food allergen

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7
Q

What are allergens?

A
  • Food proteins to which certain individuals have hypersensitivity reactions
  • Glycoproteins that are relatively resistant to digestion and cooking.
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8
Q

What are the priority food allergens in Canada?

Identified as foods that cause majority of allergic reactions in Canada

A
  • 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)
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9
Q

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

A
  • Cow’s milk
  • Soy
  • Hen’s egg
  • Peanuts
  • Tree nuts (& seeds)
  • Wheat
  • Fish
  • Shellfish
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10
Q

What is an IgE-mediated allergic reaction?

A

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

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11
Q

What are important mediators in IgE-mediated allergic reaction?

A
  • Histamine
  • Prostaglandins
  • Leukotrienes
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12
Q

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

A

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

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13
Q

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

A

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.

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14
Q

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

A
  1. Sensitization
  2. Degranulation and release of chemical mediators
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15
Q

Describe the mechanism of peanut allergy.

A

Lectin-reactive glycoproteins - IgE mediated

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16
Q

What are the symptoms of IgE-mediated allergies?

A
  • 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
17
Q

Describe acute reactions to IgE-mediated allergic reactions.

A
  • Within 2 hours after ingestion
  • Urticaria; angioedema; vomiting
18
Q

What are objective symptoms?

A
  • 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
19
Q

Describe delayed-onset IgE-mediated allergic reactions:

A
  • Within 24-72 hours after food ingestion
  • Dermatitis, infantile colic, gastro-esophageal reflux, esophagitis, diarrhea and constipation
20
Q

How are food allergy related reactions avoided?

A
  • 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.
21
Q

Are allergies outgrown?

A
  • Most children outgrow their allergy by three years of age (e.g. egg).
  • However, a severe egg allergy can last a lifetime
22
Q

Are cooked foods allergic?

A
  • 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.
23
Q

Describe peanut allergy.

A
  • 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.

24
Q

Define: NOAEL

A

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

25
Q

Define: LOAEL

A

Lowest observed adverse effect level - the lowest dose that produces an adverse effect

Range: 0.5 mg up to 8000–10,000 mg of whole peanut (Taylor et al., 2009)

26
Q

Define: population threshold.

A

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

27
Q

Discuss: dose distribution.

A
  • Record NOAEL and LOAEL dose for each of 286 subjects during 17 year long study.
28
Q

What is a food sensitivity?

A
  • A.K.A. Food intolerance
  • Adverse reaction to specific food
  • Non-immunological responses
    • Anaphylactoid reactions
    • Metabolic food disorders
    • Idiosyncratic illnesses
29
Q

What are the types of food sensitivities?

A

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

30
Q

What are anaphylactoid reactions?

A
  • 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
31
Q

What are metabolic reactions?

A
  • 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.
32
Q

Discuss lactose intolerance.

A
  • 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

33
Q

Discuss favism.

A
  • 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

34
Q

Describe idiosyncratic reactions.

A
  • 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).
35
Q

Discuss sulfite sensitivity.

A
  • 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

36
Q

Discuss sulfite-induced asthma.

A
  • 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.
37
Q

What are treatments for sulfite induced asthma?

A

Specific avoidance diet
- Read labels
- Knowledge of possible hidden allergens

Pharmacological

  • Antihistamines
  • Epinephrine, Adrenaline
  • Cortisone
38
Q

Discuss a partial list of food related idiosyncratic reactions.

Proven and unproven

A

FOOD 525 (10 decks)

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