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Immunity > Lecture 3 - Food Allergy > Flashcards

Lecture 3 - Food Allergy Flashcards

1
Q

What is the definition of a food allergy?

A

Adverse reaction to food that involves the immune system

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2
Q

What are the 2 main categories of food allergy?

A

IgE mediated
Non-IgE mediated

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3
Q

What are some examples of IgE mediated food allergies?

A

Anaphylaxis
Urticaria
Angioedema
Acute rhinitis

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4
Q

What are some examples of non-IgE mediated food allergies?

A

Contact dermatitis
Celiac disease
Heiners syndrome
FPIES

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5
Q

What is the broad process for which allergies occurs?

A

Sensitisation stage
Reaction stage

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6
Q

What is the dual allergen hypothesis for alleries occurring?

A

The way at which a patient is exposed to an antigen makes it more likely for an allergic repsonse to develop

Skin = likely allergy
Tolerance = GI exposure

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7
Q

What T helper cell usually leads to the development of allergies?

A

T Helper 2

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8
Q

Which T Helper cells usually are involved in cutaneous exposure vs oral /GI exposure?

A

Cutaneous = TH2 memory/allergy

Oral/GI = TH1 tolerance

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9
Q

What is the allergy mechanism for IgE mediated and non IgE mediated?

Sensitisation stage:

What IL are made?

A

Dendritic cells pick up allergen
MHC II presents to T Helper 2 cells
TH2 produce IL-4, IL-13 and IL-4 and IL-13 convert IgM to IgE (Class switching)
IgE binds to mast cells priming them

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10
Q

What happens once the allergen is reintroduced into the body?

A

Allergen binds to IgE on primed mast cell
Mast cell degranulates
TH2 cells proliferate making more IL-4, IL-13 and IL-5
IL-5 makes eosinophils migrate to the area

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11
Q

What activates mast cells following reintroduction of the allergen?

A

Minimum of 2 membrane bound IgE need to be cross linked by the antigen
Leading to degranulation

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12
Q

What do IL-4 and IL-13 and do?

A

Stimulate the class change of IgM to IgG

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13
Q

What is the function of IL-5?

A

Stimulates Eosinophil migration

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14
Q

What are some substances released by the degranulation of mast cells?

A

Histamine
Prostaglandins
Tryptase
Leukotrienes
IL-4 + IL-13
IL-5

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15
Q

What is the function of histamine?

A

Vasodilation
Vasopermeabilty
Bronchoconstriction
Mucus

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16
Q

What is the function of prostaglandins ?

A

Bronchoconstriction

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17
Q

What is the function of non IL-4 and 13?

A

Switch B lymphocytes to IgE

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18
Q

What are the functions of leukotrienes?

A

Bronchoconstriction
Mucus

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19
Q

What is tryptase good for measuring?

What’s it bad for measuring?

A

Good for drug allergy

Bad for food allergy

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20
Q

What are the main foods with allergens?

A

Wheat
Nuts
Soy
Shellfish
Kiwis
Milk
Eggs
Fish

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21
Q

What are the 4 main causes of non-IgE mediated food allergies?

A

Milk
Soy
Wheat
Eggs

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22
Q

What is the mnemonic used to take an allergen history?

A

EATERS

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23
Q

What does EATERS stand for when taking an allergen history?

A

Exposure
Allergen
Timing
Environment
Reproducibility (symptoms can always be triggered)
Symptoms

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24
Q

When do symptoms manifest in a patient with IgE mediated allergies?

A

Symptoms occur rapidly (within 2hrs of exposure)

25
Q

What are the red flag features of IgE mediated allergies?

A

Anaphylaxis (ABC symptoms)

26
Q

What is the most common type of non IgE mediated allergy?

A

Milk
Soya

27
Q

What are some features of non IgE mediated allergy?

Onset of symptom

A

Normally 1-72hrs after ingestion and normally occurs in less than 1 year olds

28
Q

What are some typical factors of allergies?

A

Common allergen
Urticaria
Reproducible

29
Q

What investigations can be done for food allergies?

A

sIgE (specific IgE to certain foods)
SPT (Skin prick test)

Challenge (open food challenge, single blinded challenge, double blind challenge)

30
Q

What is the point of Skin Prick Test (SPT)?

A

Reflect IgE bound to cutaneous mast cells adn subsequent release of mediators like histamine

31
Q

What is sIgE (specific IgE)?

A

Reflects sIgE within the blood

Which can indicate sensitisation not allergy

32
Q

How do specific IgE diagnostic tests work?

A

Allergen is absorbed and immobile
Patients serum is added
Allergen bound IgE is detected by enzymatically labelled anti-human IgE monoclonal antibody (brighter it is more there is)

33
Q

How does the skin prick test work?

A

Allergens injected into skin and see if a reaction occurs

Histamine injected into skin (control_

Nothing injected as a control too

34
Q

Look at slide 19, what do you think for the initial diagnosis?

A

IgE mediated milk allergy since the allergy occurs 5mins after exposure also have urticaria

35
Q

How do you test to confirm a diagnosis of IgE mediated milk allergy?

A

Specific IgE to milk

36
Q

Look at slide 24:

What is the most likely diagnosis?

A

Not likely to be IgE mediated milk allergy since happens 5hrs after exposure

Urticaria following viral infection

37
Q

Does a positive specific IgE indicate allergy?

A

No not always

38
Q

Can a baby be allergic to cows milk if they are allergic to breast milk?

A

Yes

39
Q

Start from slide 25, how do you help diagnose the milk allergy?
How long should this be done for?

A

Maternal exclusion of all milk products for at least 4 weeks (too see if symptoms improve)
Then after4 weeks give milk again to see if it worsens

40
Q

Slide 32, case 3, should egg be excluded as the cause of the allergy?

A

No since a positive result does not indicate an egg allergy

41
Q

What is angiodema?

A

Swelling of the deep tissues in the body (deeper than the skin)

42
Q

Page 36, what is the likely cause of allergens?

A

Peanut

43
Q

What do high levels of specific IgE mean?

A

Increased risk of allergy not the severity

44
Q

What is pollen food syndrome?

A

Where foods like raw apple are similar to birch pollen, birch pollen IgE attach to the apple protein

45
Q

What are some symptoms pollen food syndrome?

A

Raw apples (mild lip swelling, itchy tongue, uncomfortable throat))

46
Q

Why does pollen food syndrome barely happen with cooked foods?

A

The proteins get degraded

47
Q

What are some nuts causing pollen food syndrome?

A

Hazelnut
Peanut
Almond
Walnut
Brazil

48
Q

What are some food allergy managements?

A

Understand local dietitian services

Manage comorbitides like:
-asthma
-eczema
-Hayfever

49
Q

How to interpret:

History of acute reaction with clear identifiable trigger + Positive test?

A

Allergy

50
Q

How to interpret:

No history/unclear history of exposure/no exposure + Positive test?

A

Sensitisation

51
Q

How to interpret:

Eats the food + Positive test?

A

Sensitisation but tolerant

52
Q

How to interpret:

Positive sIgE + n reaction to food?

A

Believe the history and is fine

53
Q

How to interpret:
Negative sIgE + history of an acute reaction?

A

Believe the history, allergic

54
Q

How do you diagnose non IgE allergies?

A

Complete exclusion for 4 weeks followed by reintroduction

55
Q

What is FPIES?
(Food Protein Induced Enterocolitis syndrome)?

A

Non IgE mediated food allergy that typically presents in infancy with repetitive protracted vomiting that begins 1-4hrs after food ingestion

Diarrhoea
Dehydration
Pale, lethargic

No cutaneous and respiratory symptoms
Hypotension, hypothermia and mimic sepsis

56
Q

When does FPIES present?

A

Normally in first year of life

57
Q

What is eczema?

Treatment?

A

Inflammatory disorders

Steroids to treat

58
Q

How do we treat eczema?

A

250-500g emollient

Immunity (9 decks)

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