Immune3&4 - Food Allergy

Question 1

Important key words and definitions

Sensitivity and Hypersensitivty
Allergy and Allergen
Atopy
Anaphylaxis

Answer 1

1. ) Sensitivity - normal response to a stimulus
   - hypersensitivity is an abnormal strong response to a stimulus
2. ) Allergy - a hypersensitivity reaction initiated by a specific immunological mechanism (IgE or non-IgE)
   - an allergen is any substance stimulating the production of IgE or a cellular immune respone
3. ) Atopy - personal or familial tendency to produce IgE in response to exposure to potential allergens
   - asthma, allergic rhinitis, eczema, food allergies
4. ) Anaphylaxis - serious allergic reaction with bronchial, laryngeal, and CVS involvement
   - rapid in onset and can cause death

Question 2

8 major allergic conditions

Allergic Rhinitis/Hay Fever
Allergic Conjunctivitits
Allergic Asthma
Atopic Dermatitis/Eczema
Urticaria/Hives
Insect Allergy
Drug Allergy
Food Allergy

Answer 2

1. ) Allergic Rhinitis/Hay Fever - persistent/recurrent blocked or runny nose, itching and sneezing
   - common triggers: grass, pollens, dust mites
2. ) Allergic Conjunctivitits - red, swollen, watery, and itchy eyes (distinguishing feature)
   - often occurs w/ hay fever so similar triggers
3. ) Allergic Asthma - classical asthma symptoms:
   - wheeze, cough, SOB, tight chest
4. ) Atopic Dermatitis/Eczema - most common chronic inflammatory skin disease
   - itchy skin –> scratching –> chronic skin changes
   - triggers are rarely recognised
5. ) Urticaria/Hives - actue < 6 weeks, chronic if longer
   - common symptom of the symptom complex of acute allergic reactions
6. ) Insect Allergy - often stings from wasps or bees
   - mild: localised sting reaction w/ redness, swelling and itching around the sting site
   - severe: life-threatening anaphylaxis
7. ) Drug Allergy - less commonly reported
8. ) Food Allergy - adverse health effect arising from a specific immune response occuring on food exposure

Question 3

Food intolerance vs Food allergy

Answer 3

1. ) Primary Food Intolerance - adverse responses to foods, not involving a immune response (not allergies)
   - food characteristics: food components (e.g. caffeine), toxins from contamination
   - host characteristics: metabolic disorders, psycho… responses such as food aversion or rhinorrhoea (spicy)
2. ) Food Allergy - involves an immune mechanism
   - can be IgE or non-IgE mediated

Question 4

4 factors affecting presentation of food allergies

Age
Temperature
Food Matrix
Cross-Reactivity

Answer 4

1. ) Age - age of presentation depends on person’s diet
   - food allergy can improve or persist with ↑ age
   - improves: milk, egg, wheat, fruit
   - persists: peanut, tree nut, seed, fish, shellfish
2. ) Temperature - cooked foods have ↓ allergenicity
   - epitope structure is often damaged w/ heat
   - some epitopes are heat stable so not affected
   - e.g. 4/5 egg proteins are not heat stable
3. ) Food Matrix - interactions w/ other ingriedients in processed foods leads to lower allergenicity
   - e.g. baked milk in processed biscuits
4. ) Cross-Reactivity - food families can share proteins
   - e.g. you should test all nuts in an individual presenting with a single nut allergy

Question 5

3 features of Non-IgE mediated allergies

Common Foods x5
Presenting Age
Symptoms

Answer 5

1.) Common Foods - milk, soya, wheat, rice, meat in food protein induced enterocolitis syndrome (FPIES)

2. ) Presenting Age - infancy and early childhood
   - all milk allergies present by 1 year
   - favourable prognosis
3. ) Symptoms - vague, delayed (hours to days)
   - can mimic common GI conditions
   - resistant to medications e.g. PPIs for reflux
   - eczema is a rare presentation

Question 6

4 ways/disorders non-IgE mediated food allergies can present

Proctocolitis
Enterocolitis
Eosinophilic Oesophagitis
Food Protein Induced Enterocolitis Syndrome (FPIES)

Answer 6

1. ) Proctocolitis - passage of bright red blood in mucousy stool in an asymptomatic infant
   - milk, including breast milk
2. ) Enterocolitis - multiple, varying GI symptoms:
   - feed refusal, persistent vomiting, abdominal cramps, loose and frequent stools, constipation
   - milk, eggs, wheat
3. ) Eosinophilic Oesophagitis - eosinohphils deposit in the lining of the oesophagus –> inflammation
   - feeding disorders, reflux, dysphagia, food impaction
   - milk, eggs, wheat
4. ) Food Protein Induced Enterocolitis Syndrome
   - infants w/ profuse vomiting –> pallor, lethargy
   - milk, soya, rice, wheat, meat

Question 7

3 features of IgE mediated allergies

Common Foods x5
Presenting Age
Symptoms

Answer 7

1.) Common Foods - milk, eggs, nuts, fish, fresh fruit and vegetable

2. ) Presenting Age - depends on age of contact
   - all milk allergies present by 1 year
   - milk and egg allergy can resolve whilst others persist
3. ) Symptoms - immediate (5-30 mins)
   - affects the skin, GI tract, CVS and respiratory system

4.) Specific Disorders - how it presents

Question 8

Symptoms of IgE mediated food allergies

Skin x4
GI x5
Respiratory System (URT x6, LRT x3) 
Cardiovascular System x3
Other x3

Answer 8

1. ) Skin - pruritis, erythema, acute urticaria
   - angioedema (lips, face, eyes)
2. ) GI - oral pruritis, angioedema (lips, tongue, palate)
   - N/V, diarrhoea, colicky abdominal pain
3. ) Respiratory System
   - URT: runny and/or blocked, itchy nose, sneezing, croupy cough, stridor
   - LRT: SOB, cough, wheeze
4. ) Cardiovascular System - uncommon
   - hypotension, pallor, drowsy
5. ) Other - behavioural changes:
   - mood changes, agitation, sense of impending doom

Question 9

4 ways/disorders IgE mediated food allergies can present

Urticaria/Angioedema
Pollen Food Syndrome
Anaphylaxis
Food-Associated Exercise Induced Anaphylaxis

Answer 9

1. ) Urticaria/Angioedema - acute hives w/ swelling and nausea and vomiting, no respiratory symptoms
   - occurs in 170+ foods
2. ) Pollen Food Syndrome - pruritus and mild oedema of the oral cavity, often doesn’t progress any further
   - most common food allergy in adults as it’s a result of cross-reactivity between pollens of:
   - uncooked fruit, vegetables, nuts
3. ) Anaphylaxis - have respiratory and CVS symptoms
   - nuts, fish, shellfish, celery
4. ) Food-Associated Exercise Induced Anaphylaxis
   - food triggers anaphylaxis only if ingestion is followed by exercise (within 2 hours)
   - wheat, shellfish, celery

Question 10

Diagnosis of food allergies

Context of Reaction x6
Presenting Symptoms
Physical Examination
Skin Prick Tests
Blood Tests

Answer 10

1. ) Context of Reaction
   - age, suspected foods, route of exposure
   - activity at time of exposure e.g. exercise or alcohol
   - any current illnesses at time of reaction
   - foods eaten previously without symptoms
2. ) Presenting Symptoms
   - ask symptoms from all systems
   - timing and duration (immediate or delayed?)
   - treatment provided and response to treatment
3. ) Physical Examination - most patients present to an outpatient clinic, after signs are long resolved
   - examine for other allergic condtions
4. ) Skin Prick Tests - reponse of skin mast cells
   - ↑sensitivty –> ↑ likelihood of having an allergy
   - very fast, can produce information in 15 minutes
   - oral food challenges done to confirm diagnosis
5. ) Blood Tests - looks at IgE Abs circulating in blood
   - tests for IgE Abs for sensitivty rather than allergy
   - ↑sensitivty –> ↑ likelihood of having an allergy

Question 11

4 ways to manage food allergies

Anticipatory Allergy Testing
Dietary Exclusions
Early Food Introductions in Infancy
Desensitisation to Food Allergens

Answer 11

1. ) Anticipatory Allergy Testing
   - testing for cross-reactive allergens and potential future allergens to minimise dietary exclusions

2.) Dietary Exclusions - only need to avoid foods that are not tolerated rather than whole classes of foods

3. ) Early Food Introductions in Infancy
   - exposed to lower allergenic forms of foods e.g. baked milk/eggs to accelerate further tolerance
4. ) Desensitisation to Food Allergens
   - used in children w/ milk and egg allergies that do not resolve as expected, to induce tolerance to the allergies
   - also available for peanut allergies

Question 12

How to use an Epi-Pen

Answer 12

Removal of the safety cap
Placement of device against mid-anterolateral thigh
Injection until a click is heard
hold in place for 3-10 seconds
massage injection site for 10 seconds