Food Allergies and Sensitivities Flashcards
Prevalence of food allergies is based on:
Prevalence of food allergies is based on self-or parental diagnosis, or clinical impressions without complete medical diagnosis.
What is the range of food allergies and sensitivies?
- 0.3-7.5% general population
- 4-6% infants
- 1-2% young children
- <1% adults
Define: true food allergy
The immunologically mediated adverse reactions resulting from the ingestion of a food or food additive.
What are the causes of true food allergy? [4]
- Heredity (atopic disease)
- Naturally occurring substances in foods (e.g., mostly proteins)
- Food additives (e.g., papain enzyme - a component of meat tenderizers)
- Food contaminants (e.g., penicillin residues
What are the mechanisms of true food allergy? [4]
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
Define: food allergy.
Immune-mediated inflammatory response to food allergen
What are allergens?
- Food proteins to which certain individuals have hypersensitivity reactions
- Glycoproteins that are relatively resistant to digestion and cooking.
What are the priority food allergens in Canada?
Identified as foods that cause majority of allergic reactions in Canada
- 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)
More than 90% of IgE-mediated food allergies are caused by:
- Cow’s milk
- Soy
- Hen’s egg
- Peanuts
- Tree nuts (& seeds)
- Wheat
- Fish
- Shellfish
What is an IgE-mediated allergic reaction?
A food allergy that is mediated by food-specific immunoglobulin E (IgE) antibodies.
What are important mediators in IgE-mediated allergic reaction?
- Histamine
- Prostaglandins
- Leukotrienes
What is the first event of IgE-mediated allergic reaction?
Sensitization - once the allergen is consumed, sensitization of the individual results in the production of allergen-specific IgE antibodies.
What is the second event of IgE-mediated allergic reaction?
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.
What are the two steps of IgE-mediated allergic reaction?
- Sensitization
- Degranulation and release of chemical mediators
Describe the mechanism of peanut allergy.
Lectin-reactive glycoproteins - IgE mediated
What are the symptoms of IgE-mediated allergies?
- 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
Describe acute reactions to IgE-mediated allergic reactions.
- Within 2 hours after ingestion
- Urticaria; angioedema; vomiting
What are objective symptoms?
- 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
Describe delayed-onset IgE-mediated allergic reactions:
- Within 24-72 hours after food ingestion
- Dermatitis, infantile colic, gastro-esophageal reflux, esophagitis, diarrhea and constipation
How are food allergy related reactions avoided?
- 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.
Are allergies outgrown?
- Most children outgrow their allergy by three years of age (e.g. egg).
- However, a severe egg allergy can last a lifetime
Are cooked foods allergic?
- 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.
Describe peanut allergy.
- 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.
Define: NOAEL
No observed adverse effect level - the highest dose that will not produce any adverse effect in that person
Define: LOAEL
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)
Define: population threshold.
The largest amount of peanut that would not cause an adverse reaction in any individual within the total population of peanut-allergic individuals.
Discuss: dose distribution.
- Record NOAEL and LOAEL dose for each of 286 subjects during 17 year long study.
What is a food sensitivity?
- A.K.A. Food intolerance
- Adverse reaction to specific food
-
Non-immunological responses
- Anaphylactoid reactions
- Metabolic food disorders
- Idiosyncratic illnesses
What are the types of food sensitivities?
1) Anaphylactoid
2) Metabolic deficiency of enzyme(s)
3) Idiosyncratic
What are anaphylactoid reactions?
- 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
What are metabolic reactions?
- 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.
Discuss lactose intolerance.
- 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
Discuss favism.
- 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
Describe idiosyncratic reactions.
- 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).
Discuss sulfite sensitivity.
- 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
Discuss sulfite-induced asthma.
- 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.
- Level in foods will vary from
What are treatments for sulfite induced asthma?
Specific avoidance diet
- Read labels
- Knowledge of possible hidden allergens
Pharmacological
- Antihistamines
- Epinephrine, Adrenaline
- Cortisone
Discuss a partial list of food related idiosyncratic reactions.
Proven and unproven
