Food allergies

Question 1

Briefly describe the two main types of allergies, and give an example of an allergen for each. (6)

Answer 1

IgE mediated - immediate onset - peanut.

Non-IgE mediated - delayed onset - milk.

Question 2

Define allergy. (2)

Answer 2

Immunological hypersensitivity that can lead to disease process.

Question 3

Define allergen. (3)

Answer 3

Any substance stimulating the production of IgE or a cellular immune response. Can be a carbohydrate, but normally a protein.

Question 4

Define sensitivity. (1)

Answer 4

Normal response to a stimulus.

Question 5

Define hypersensitivity. (1)

Answer 5

Abnormally strong response to a stimuli.

Question 6

Define sensitisation. (1)

Answer 6

Production of IgE antibodies after repeated exposure to an antigen.

Question 7

Define atopy. (3)

Answer 7

A tendency in an individual to produce IgE in response to ordinary exposure to potential allergens. Strongly associated with roof allergy, eczema, asthma and rhinitis.

Question 8

Define anaphylaxis. (3)

Answer 8

A serious allergic reaction with bronchial, laryngeal and cardiovascular involvement which is rapid in onset and can cause death.

Question 9

Define food allergy. (3)

Answer 9

An adverse health effect arising to a specific immune response that occurs reproducibly on exposure to a food. Can be IgE mediated or not.

Question 10

Define food intolerance. (2)

Answer 10

Numerous adverse responses to food that do not involve an immune response.

Question 11

Define “allergic rhinitis”. (2)

Answer 11

Blocked / runny nose, sneezing, triggered by allergens eg pollen pets.

Question 12

Define “allergic conjunctivitis”. (1)

Answer 12

Red, swollen, itchy eyes.

Question 13

Describe asthma. (2)

Answer 13

Chest symptoms of breathlessness, cough, wheeze, tight chest. Not always allergic.

Question 14

Define “atopic dermatitis”. (3)

Answer 14

Commonly known as eczema, a common chronic inflammatory skin disease with itch and excoriation.

Question 15

Define urticaria. (3)

Answer 15

Commonly known as hives, a macula-papular rash that can be acute or chronic and present with out without angioedema.

Question 16

Describe the differences between IgE mediated allergies and Non-IgE mediated allergies in terms of symptom onset. (4)

Answer 16

IgE - immediate 5-30 minutes

Non-IgE - delayed hours to days.

Question 17

Describe the differences between IgE mediated allergies and Non-IgE mediated allergies in terms of presenting age. (2)

Answer 17

Both variable depending on age at contact, all milk by 1 year.

Question 18

Describe the differences between IgE mediated allergies and Non-IgE mediated allergies in terms of common foods affected. (4)

Answer 18

IgE - milk, eggs, nuts, peanuts, fish, shellfish, fruit, veg.
Non-IgE - milk, soya, wheat, rice, oats.

Question 19

Describe the differences between IgE mediated allergies and Non-IgE mediated allergies in terms of resolution. (2)

Answer 19

IgE - some resolve, some persist into adulthood.

Non-IgE - resolve earlier than IgE, often by school age.

Question 20

Describe the common skin reactions in IgE mediated reactions. (4)

Answer 20

Pruritus
Erythema
Acute urticaria
Acute angioedema - lips, face, eyes.

Question 21

Describe the common GI reactions in IgE mediated reactions. (4)

Answer 21

Angioedema- lips, tongue, palate.
Nausea and vomiting
Diarrhoea
Colicky abdominal pain

Question 22

Describe the common respiratory reactions in IgE mediated reactions. (4)

Answer 22

Blocked / runny nose
Sneeze
Wheeze
Cough

Question 23

Describe the common cardiovascular reactions in IgE mediated reactions. (3)

Answer 23

Pallor
Drowsiness
Hypotension

Question 24

Describe the common skin reactions in non-IgE mediated reactions. (2)

Answer 24

Pruritus 
Eczema (esp atopic that doesn’t respond to treatment)

Question 25

Describe the common GI reactions in non-IgE mediated reactions. (6)

Answer 25

Abdominal pain
Food aversion or reversal 
GORD (esp that doesn’t respond to treatment)
Diarrhoea or constipation 
Blood or mucus in stools 
Perianal redness

Question 26

Describe the common CVS reactions in non-IgE mediated reactions. (2)

Answer 26

Pallor

Tiredness

Question 27

Describe the common systemic reactions in non-IgE mediated reactions. (1)

Answer 27

Faltering / stunted growth.

Question 28

Name four common phenotypes of IgE mediated food allergies. Describe them, and list what allergen is common for causing them. (12)

Answer 28

Urticaria / angioedema - acute hives with swelling and GI symptoms, but no resp or CVS symptoms - any allergen.
Anaphylaxis - rapidly progressive, fatal, multi-organ - nuts, fish, shellfish, milk, eggs
Food-associated exercise induced anaphylaxis - food triggers anaphylaxis only if followed within 2 hours by exercise - wheat, shellfish, celery.
Pollen food syndrome - pruritus and oedema confined to the oral cavity, associated with hay fever - RAW fruit or veg.

Question 29

Describe four common phenotypes of non-IgE mediated food allergies. Describe them, and list what allergen is common for causing them. (14)

Answer 29

Protocolitis - bright red blood in stools in asymptomatic infants - breast milk.
Enterocolitis - GI symptoms (refusal, vomiting, cramps, diarrhoea/constipation) - milk, eggs, wheat.
Eosinophilic oesophagitis - oesophageal inflammation and scarring, causing reflux, vomiting, dysphagia and impaction. Diagnosed with endoscopy and biopsy for eosinophils - milk, eggs, wheat.
Food-protein induced enterocolitis Syndrome - profuse vomiting and diarrhoea leading to pallor, lethargy and shock. Can be mistaken for sepsis, drip with temporarily relieve symptoms, but they will recur - milk, soya, rice, wheat, meat.

Question 30

Describe the effects of cooking on the allergenicity of these products: 
Cows milk 
Egg whites
Peanut
Fish
Apple
(8)

Answer 30

Milk: heat destroys whey but not casein. Forms bonds when in a matrix eg milky biscuit.
Egg: well cooked egg eg in baked goods much less allergic.
Peanut: increased if roasted, decreased if boiled.
Fish: proteins very heat stable, but canning reduces allergenicity.
Apple: very heat sensitive.

Question 31

Explain why some milk proteins are destroyed by heating and some are not. (2)

Answer 31

Heating only destroys conformational proteins, not sequential ones.

Question 32

Describe cross reactivity. (2)

Answer 32

If a patient is allergic to one thing (eg cows milk) they are likely to be allergic to a similar thing (eg goats milk).

Question 33

Describe the presentations of a milk allergy. (4)

Answer 33

IgE mediated:
- urticaria, cough, wheeze, vomiting + diarrhoea.
- can cause anaphylaxis and be fatal.
Non-IgE mediated:
- GORD, constipation, pain, refusal.
- difficult to diagnose because can present like reflux and colic.

Question 34

Describe the things that make a milk allergy be suspected in an infant. (3)

Answer 34

Formula fed from birth and fussy.
If they’ve tried feed thickeners, high dose antacids, “lactose free” formula and the symptoms haven’t improved, suspect milk allergy.

Question 35

Describe the alternative formula options that are available to a baby with a milk allergy. (10)

Answer 35

Amino acid - plant based, allergen free but expensive.
Extensively hydrolysed - altered cows milk; could still be allergic, but cheap and encourages resistance.
Soya - good for over 6 months, but needs fortification.
Goats milk - not advised; cross reactivity common.
Lactose free - they have a milk protein allergy, not a lactose allergy so still allergic.

Question 36

Describe the “milk ladder”. (4)

Answer 36

A process of reintroduction of milk into a child’s diet. 
1 - small bit of milk biscuits. 
2 - cakes, butter
3 - cooked cheese, custard, chocolate
4 - raw cheese, ice cream, UHT milk
5 - pasteurised milk

Question 37

Explain the need for a thorough food history when suspecting food-induced anaphylaxis. (2)

Answer 37

Helps you to rule in or out foods that they have / haven’t been exposed to in the past. Eg if they regularly eat eggs it won’t be an egg allergy, but if this is the first time they’ve tried shellfish it might be.

Question 38

Name 5 of the 14 common allergens. (5)

Answer 38

Celery, cereals, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, peanuts, sesame seeds, soya, sulphur dioxide.

Question 39

Explain the importance of dietary inclusions and exclusions when diagnosed with an allergy. (4)

Answer 39

Must exclude food that they are been diagnosed as having an allergy to as best they can.
Must eat a wide range of other foods (inclusions) so more allergies do not develop.

Question 40

Describe the difficulties with exclusion criteria in severe allergies (2)

Answer 40

Eating out / take always are not always detailed. Especially hard with “may contain traces”

Question 41

Describe the steps taken when a patient presents looking to know if their eczema is caused by a food allergy. (4)

Answer 41

Total IgE and SPTs.
If the patient has no positive SPTs, no asthma or hay fever, and no known allergies, it is not a food allergy-induced eczema.
Check compliance with emollient and steroid treatments.

Question 42

Describe the process of diagnosing a food allergy. (4)

Answer 42

Medical history - context, presentation, food history
Physical examination
Screening tests
Diagnostic verification - oral food challenges

Question 43

Describe the important features to highlight when asking about the context of an allergic reaction. (5)

Answer 43

Age at onset
Complete list of all foods suspected
Route of exposure
Activity at the time of exposure
Any intercurrent illness at the time of reaction
List of foods previously ingested with no reaction.

Question 44

Describe the important features to highlight when asking about the symptoms of an allergic reaction. (5)

Answer 44

All observed symptoms and the severity of each
Timing of symptom onset in relation to time of exposure
Duration of symptoms
Any treatment given, and response to that treatment.

Question 45

Describe the important features to highlight when asking about the food related factors of a presenting food allergy. (2)

Answer 45

Manner of food preparation - raw, cooked, added ingredients

Minimal quantity of food needed to get a reaction.

Question 46

Describe the process of SPT. (5)

Answer 46

Skin prick testing involves pricking the skin with a needle through a solution of allergen. If there is a positive test, the area will become swollen due to mast cell response.
Responses are scored from 0 (no reaction) to 10 (very sensitive).

Question 47

Describe the process of immunoassay. (4)

Answer 47

Most commonly using Western Blotting or ELISA testing. Tests for specific IgE to that allergen and total IgE, but not all sensitivity indicated allergy, and it cannot assess the severity of reaction.