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Sem 4: Immunity > 2a.) Food Allergy > Flashcards

2a.) Food Allergy Flashcards

1
Q

Is allergy common?

A

Yes, for example:

  • Allergic rhinitis (such as in hayfever) affects up to 30% adults
  • Asthma diagnosed in >1 in 10 school children
  • Food allergy is confirmed in about 6% children
  • Nearly half of all UK adults suffer from at least one allergy
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2
Q

Is allergy associated with significant morbidity?

A

Yes as allergy an lead to:

  • Persistant symptoms can impair sleep & reduce productivity
  • Recurrent hosp admissions for asthma cause high absenteeism
  • Restrictive diets can cause social exclusion & malnutrition
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3
Q

Can allergy be fatal?

A

Yes:

  • 1200 people die from asthma in UK per year
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4
Q

Is allergy a disease itself?

A

No, but it is a mechanism leading to a disease

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5
Q

Define allergy

A
  • Immunological hypersensitivity that can lead to a variety of different diseases via different pathomechanisms with different approaches in diagnosis, therapy & prevention

OR

  • A hypersensitivity reaction initiated by specific immunological mechanisms. This can be IgE mediated (e.g. peanut allergy) or non-IgE mediated (e.g. milk allergy)
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6
Q

Define the term ‘allergen’

A

Any substance stimulating the production of IgE or a cellular immune response. Usually a protein but can be carbohydrates (much less common)

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7
Q

Define sensitivity

A

Normal response to stimulus

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8
Q

Define hypersensitivity

A

Abnormally strong response to stimuli

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9
Q

Define sensitisation

A

Production of IgE antibodies (detected by serum IgE assay or SPT) after repeated exposure to an allergen

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10
Q

Define atopy

A

A tendancy to produce IgE antibodies in response to ordinary exposure to potential allergens. Strongly associated with asthma, rhinitis, eczema & food allergy

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11
Q

Define anaphylaxis

A

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

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12
Q

Define food (in terms of what we class as food in the allergy terms)

A

A substance, whether processes, semi-processed or raw which is intended for human consumption (including drinks) and any substance used in manufacture, preparation or treatment of food

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13
Q

Define food allergy

A

An adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a good. Definition encompasses immune responses that are IgE mediated or non-IgE mediated

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14
Q

State, and describe the presentation of, the 8 major allergic diseases

A
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15
Q

Discuss the prevalence of allergic diseases with age, include:

  • Eczema
  • Food allergy
  • Asthma
  • Rhinoconjuctivitis
  • Any allergy
A
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16
Q

What is the ‘allergic march’?

Describe the shape of the allergic march for each of the following:

  • Eczema
  • Asthma
  • Food allergy
  • Rhinitis
A

The typical progression/development of allergic diseases, that start early in life, over time

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17
Q

What is the commonest food allergy in infants?

A

Milk allergy (2-3%)

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18
Q

By what age does milk allergy ALWAYS present by?

A

12 months (hence if after 12 months then not milk allergy)

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19
Q

State and describe the two types of presentation of milk allergy

A

*NOTE: for delayed onset this means symptoms can present many weeks after milk first ingested

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20
Q

State the 14 major allergens which are responsible for 90% of immediate onset reactions in UK

A
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21
Q

Define food intolerance

A

Numerous (frequently reported) adverse responses to foods that do not involve an immune reponse

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22
Q

Is the prevalence of self-reported food allergy high than proven allergy?

A
23
Q

Discuss how we can classify adverse food reactions

A
24
Q

Food allergies can be IgE mediated or non-IgE mediated, compare the two including:

  • Onset of symptoms
  • Common foods
  • Presenting age
  • Typical progression of allergy
A
25
Q

Food allergies can be IgE mediated or non-IgE mediated; compare symptoms/presentations of each

A
26
Q

What is anaphylaxis?

A

Severe, potentially life-threatening, allergic reaction with multiple organ system reaction including respiratory, cardiovascular etc…

27
Q

What is food-associated exercise induced anaphylaxis?

A

Food triggers anaphylaxis only if ingestion is followed temporally (within 2 hours) by exercise. Occurs wtih wheat, shellfish, celery

28
Q

What is pollen food syndrome?

A

Pruritus & mild oedema confined to oral cavity (lips, tongue, mouth & throat) uncommonly progressing. Associated with hayfever (raw fruits & vegetables)

29
Q

Delayed onset/non-IgE mediated food allergies can present as protocolitis; what is protocolitis?

A
30
Q

Delayed onset/non-IgE mediated food allergies can present as enterocolitis; what is enterocolitis?

A
31
Q

Delayed onset/non-IgE mediated food allergies can present as eosinophilic oesophagitis; what is eosinophilic oesophagitis?

A
32
Q

Delayed onset/non-IgE mediated food allergies can present as food protein-induced enterocoltis syndrome; what is food protein induced enterocolitis syndrome?

A
33
Q

Describe the food allergy march for the following foods:

  • Milk
  • Egg
  • Peanuts
  • Others such as wheat, tree nuts, fish, sesame, soya
  • Fresh fruit & vegetables
A
34
Q

Temperatures can alter the proteins in foods and hence make them less or more allergenic; true or false?

A

True

35
Q

Can patients who have milk allergy tolerate baked milk such as that in wheat?

A
  • Milk has two proteins; casein & whey
  • Casein more heat resistant thatn whey
  • However, some bonds broken/proteins are altered by heat
  • So up to 70% milk-allergic can tolerate baked milk such as that in wheat
36
Q

Can patients who have egg allergy tolerated well cooked egg?

A
  • 4 major proteins in egg; all are heat labile except ovomucoid
  • So up to 70% of egg-allergic can tolerate well cooked egg (e.g. in wheat)
37
Q

Discuss how the allergenicity of peanuts changes with different types of cooking

A
  • Dry roasted: increase
  • Boil or fry: decrease
38
Q

Can patients who have fish allergy tolerate cooked fish?

A

Fish proteins are very heat stable so probably not no; however, canned tuna & salmon are significantly less allergic

39
Q

Dicuss whether patients with pollen food syndrome can eat processed/cooked apple?

A
  • Apples are very heat sensitve
  • So yes, they can tolerate processed/cooked apple
40
Q

What do we mean when we talk about cross-reactive food allergens?

A

Idea that proteins in one food are similar to proteins in another hence if you are allergic to one you are likely to be allergic to the other

41
Q

State some examples of cross-reactive food allergens (e.g. if you are allergic to ___ you are most likely allergic to____)

A
42
Q

Discuss the 4 main stages in diagnosing a food allergy

A

Context

  • Age of onset
  • List of all foods suspected to cause symptoms
  • Route of exposure (e.g. ingestion, inhalation, skin contact etc…)
  • Activity at time of expsosure (exercise or alcohol cna potentiate)
  • Any other illness at time of reaction (that may mimic allergic reaction)
  • List of foods previously ingested without symptoms

Symptoms

  • All observed symptoms and the severity of each
  • Timing of symptom onset
  • Duration of symptoms, treatmetn provided, response to treatment

Food

  • Manner in which food was prepared (cooked, raw, added ingredients etc…)
  • Minimal qunatitiy of food exposure required to cause symptoms
43
Q

Describe how you do a skin prick test to detect allergen-specific IgE

A

You are lookign for response of skin mast cells to allergens

44
Q

Dicuss how immunoassays work to detect allergen-specific IgE

A
45
Q

Skin prick tests & serum specific IgE are used to detect allergen-specific IgE.

What does the levle of sIgE or size of SPT test you?

A
  • Tells you/correlates with likelihood of allergy
  • It determines presence of sensitivity not allergy
  • It does not correlate with or predict severity of allergic reaction

*Hence, you determine if true allergy by combining results with clinical hisotry, possible cross-reactivity and targetting possible allergens and looking for improvement

46
Q

Explain why we only do sIgE immunoassays if there is an allergy focused clinical history

A
47
Q

Discuss how we manage food allergy

A
  • Exclusions of foods
  • Inclusion of foods
  • Label reading (both ingredients & advisory)
  • Food reintroductions
  • Medical advice e.g. emergency management of allergic/anaphylactic reaction
48
Q

Read this case study and decide whether the baby has a milk allergy and if so is it IgE mediated or non-IgE mediated; explain your answers. Note: baby did not respond to feed thickner or antacid

A
49
Q

Discuss how we manage milk allergy in infants

A
  • Replace breast milk/normal milk formula with extensive hydrolysed formula (still contants small amount of milk protein)
  • If above doesn’t work, try amino acid formula as has no milk protein (it is derived from plant proteins)
  • At 6 months can try soya milk
  • Dairy free weaning advice and milk reintroduction to hopefully get rid of allergy
50
Q

Lactose is specific to mamallian milk; true or false?

A

True

51
Q

Briefly describe the ‘milk ladder’

A
52
Q

Read the following case study and decide whether the child has a food allergy and if so is it IgE or non-IgE mediated?

A
53
Q

Read the following case and decide whether child has allergy and if so whether it is IgE or non-IgE mediated.

NOTE: his skin prick tests to foods and nuts all negative

A

Food allergy is not causing eczema. This is idea that if we test when not relevant clinical history we get false positives.

Sem 4: Immunity (6 decks)

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