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Y2 - Immunity > Lecture 3 - Food Allergy > Flashcards

Lecture 3 - Food Allergy Flashcards

(58 cards)

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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?

Study These Flashcards
A

Symptoms occur rapidly (within 2hrs of exposure)

25
What are the red flag features of IgE mediated allergies?
Anaphylaxis (ABC symptoms)
26
What is the most common type of non IgE mediated allergy?
Milk Soya
27
What are some features of non IgE mediated allergy? Onset of symptom
Normally 1-72hrs after ingestion and normally occurs in less than 1 year olds
28
What are some typical factors of allergies?
Common allergen Urticaria Reproducible
29
What investigations can be done for food allergies?
sIgE (specific IgE to certain foods) SPT (Skin prick test) Challenge (open food challenge, single blinded challenge, double blind challenge)
30
What is the point of Skin Prick Test (SPT)?
Reflect IgE bound to cutaneous mast cells adn subsequent release of mediators like histamine
31
What is sIgE (specific IgE)?
Reflects sIgE within the blood Which can indicate sensitisation not allergy
32
How do specific IgE diagnostic tests work?
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
How does the skin prick test work?
Allergens injected into skin and see if a reaction occurs Histamine injected into skin (control_ Nothing injected as a control too
34
Look at slide 19, what do you think for the initial diagnosis?
IgE mediated milk allergy since the allergy occurs 5mins after exposure also have urticaria
35
How do you test to confirm a diagnosis of IgE mediated milk allergy?
Specific IgE to milk
36
Look at slide 24: What is the most likely diagnosis?
Not likely to be IgE mediated milk allergy since happens 5hrs after exposure Urticaria following viral infection
37
Does a positive specific IgE indicate allergy?
No not always
38
Can a baby be allergic to cows milk if they are allergic to breast milk?
Yes
39
Start from slide 25, how do you help diagnose the milk allergy? How long should this be done for?
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
Slide 32, case 3, should egg be excluded as the cause of the allergy?
No since a positive result does not indicate an egg allergy
41
What is angiodema?
Swelling of the deep tissues in the body (deeper than the skin)
42
Page 36, what is the likely cause of allergens?
Peanut
43
What do high levels of specific IgE mean?
Increased risk of allergy not the severity
44
What is pollen food syndrome?
Where foods like raw apple are similar to birch pollen, birch pollen IgE attach to the apple protein
45
What are some symptoms pollen food syndrome?
Raw apples (mild lip swelling, itchy tongue, uncomfortable throat))
46
Why does pollen food syndrome barely happen with cooked foods?
The proteins get degraded
47
What are some nuts causing pollen food syndrome?
Hazelnut Peanut Almond Walnut Brazil
48
What are some food allergy managements?
Understand local dietitian services Manage comorbitides like: -asthma -eczema -Hayfever
49
How to interpret: History of acute reaction with clear identifiable trigger + Positive test?
Allergy
50
How to interpret: No history/unclear history of exposure/no exposure + Positive test?
Sensitisation
51
How to interpret: Eats the food + Positive test?
Sensitisation but tolerant
52
How to interpret: Positive sIgE + n reaction to food?
Believe the history and is fine
53
How to interpret: Negative sIgE + history of an acute reaction?
Believe the history, allergic
54
How do you diagnose non IgE allergies?
Complete exclusion for 4 weeks followed by reintroduction
55
What is FPIES? (Food Protein Induced Enterocolitis syndrome)?
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
When does FPIES present?
Normally in first year of life
57
What is eczema? Treatment?
Inflammatory disorders Steroids to treat
58
How do we treat eczema?
250-500g emollient

Y2 - Immunity (9 decks)

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