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MK - (LUSUMA) Immune System > S2) Food Allergy > Flashcards

S2) Food Allergy Flashcards

1
Q

Define allergy

A
  • Allergy is an immunological hypersensitivity that can lead to a variety of different diseases via different pathomechanisms
  • It has different approaches in diagnosis therapy and prevention
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2
Q

Is an allergy a disease?

A

Allergy is not a disease itself, but a mechanism leading to disease.

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3
Q

Define allergen

A
  • An allergen is any substance stimulating the production of IgE or a cellular immune response.
  • Usually a protein, but can be carbohydrates
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4
Q

Define sensitivity

A

Sensitivity is a normal response to a stimulus.

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5
Q

Define hypersensitivity

A

Hypersensitivity is an abnormally strong response to a stimulus.

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6
Q

Define sensitisation

A

Sensitisation is the production of IgE antibodies after repeated exposure to an allergen.

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7
Q

Define atopy

A
  • Atopy is a tendency to produce IgE antibodies in response to ordinary exposure to potential allergens.
  • Strongly associated with asthma, rhinitis, eczema and food allergy.
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8
Q

Define anaphylaxis

A

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

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9
Q

There are 8 possible presentations of allergy. Identify them

A
  • Allergic rhinitis
  • Allergic conjuctivitis
  • Asthma
  • Atopic dermatitis / eczema
  • Urticaria
  • Insect allergy
  • Food allergy
  • Drug allergy
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10
Q

Allergic rhinitis is also called hay fever. Identify its symptoms and triggers

A
  • Symptoms: blocked/runny nose, itchy nose, sneezing.
  • Triggers: pollen, pets or HDM.
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11
Q

Allergic conjuctivitis can occur with allergic rhinitis. Identify its symptoms

A

Symptoms: red, swollen, itchy, watery eyes.

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12
Q

Asthma is not always allergic but its symptoms are the same. Identify them

A

Symptoms: wheeze, cough, shortness of breath and tight chest

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13
Q

What is atopic dermatitis/eczema?

A

Atopic dermatitis is the commonest chronic inflammatory skin disease with itch and excoriation

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14
Q

What is urticaria?

A

Urticaria is an acute/chronic (±6w) maculo‐papular pruritic rash with/without angioedema

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15
Q

Insect allergy is usually to bee/wasp stings. What are its different forms of presentation?

A
  • Mild (local)
  • Moderate (urticaria)
  • Severe (anaphylaxis)
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16
Q

Why is allergy important?

A
  • Allergy is common
  • Allergy is associated with significant morbidity
  • Allergy can be fatal
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17
Q

How exactly is allergy common? Provide three examples

A
  • Approx. 50% of UK adults have at least 1 allergy
  • Allergic rhinitis affects up to 30% of adults.
  • Asthma is diagnosed in more than 10% UK children
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18
Q

Define food

A
  • Food is a substance, whether processed, semi‐processed or raw, which is intended for human consumption
  • It is also any substance used in the manufacture, preparation or treatment of food.
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19
Q

Define food allergy

A

Food allergy is an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a food.

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20
Q

Define food intolerance

A

Food intolerance are numerous adverse responses to foods that do not involve an immune response.

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21
Q

What are the 3 most common food allergies?

A
  • Milk
  • Eggs
  • Peanuts
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22
Q

Identify three ways in which allergy is associated with significant morbidity

A
  • AR can impair sleep and reduce productivity
  • Hospital admissions for asthma cause high absenteeism
  • Restrictive diets in food allergy cause social exclusion and malnutrition
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23
Q

Identify and describe the 2 types of adverse food reactions

A
  • Non‐immune mediated: primary food intolerances
  • Immune mediated: food allergy and coeliac disease
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24
Q

What are the two types of immune mediated adverse food reactions?

A
  • IgE mediated
  • Non‐IgE mediated
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25
Q

What are the characteristics of food causing non-immune mediated adverse reactions?

A
  • Pharmacologic eg. caffeine
  • Toxic eg. scromboid fish toxin
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26
Q

What are the host characteristics in non-immune mediated adverse food reactions?

A
  • Psychological eg. food adversion
  • Metabolic eg. lactose intolerance
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27
Q

For IgE-mediated food reactions, describe the following:

  • Symptom onset
  • Common foods
  • Presenting age
A
  • Symptom onset: immediate (5‐30 min)
  • Common foods: milk, egg, nuts, shellfish
  • Presenting age: variable, depends on contact
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28
Q

Do all IgE-mediated allergies last a lifetime?

A
  • PFS is detected in adolescence and milk allergy by 1st year
  • Milk and egg allergies can resolve while others persist into adulthood
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29
Q

For non IgE-mediated food reactions, describe the following:

  • Symptom onset
  • Common foods
  • Presenting age
  • Natural History
A
  • Symptom onset: delayed (hours - days)
  • Common foods: milk, soya, wheat, rice & oats
  • Presenting age: infancy and early childhood
  • Natural history: resolve earlier than IgE
30
Q

How can IgE-mediated food allergies present in the skin?

A
  • Pruritus, erythema
  • Acute urticaria
  • Acute angioedema (lips, face, eyes)
31
Q

How can IgE-mediated food allergies present in the Gastrointestinal system?

A
  • Angioedema (lips, tongue,palate)
  • Oral pruritus
  • Nausea, vomiting, diarrhoea
32
Q

How can IgE-mediated food allergies present in the respiratory system?

A
  • Upper resp: blocked/runny nose, sneeze, itch
  • Lower resp: wheeze, cough
33
Q

How can IgE-mediated food allergies present in the Cardiovascular system?

A
  • Pallor
  • Drowsiness
  • Hypotension
34
Q

How can non IgE-mediated food allergies present in the skin?

A
  • Pruritis
  • Eczema
  • Atopic eczema
35
Q

How can non IgE-mediated food allergies present in the Gastrointestinal system?

A
  • Loose or frequent stools
  • Blood and/or mucus in stools
  • Abdominal pain
  • Food refusal/aversion
  • Constipation
36
Q

Identify 4 different presentations of IgE-mediated adverse food reactions

A
  • Acute urticaria/angioedema
  • Anaphylaxis
  • Pollen‐food syndrome (PFS)
  • Food‐associated exercise‐induced anaphylaxis
37
Q

When does Food‐associated exercise induced anaphylaxis occur?

A
  • Food triggers anaphylaxis only if ingestion is followed temporally (within 2 hours) by exercise.
  • Involves wheat, shellfish, celery
38
Q

Identify some symptoms of Pollen Food Syndrome.

What is it associated with?

A
  • Symptoms: pruritus and mild oedema confined to the oral cavity
  • Associated with hay fever (raw fruit and vegetables)
39
Q

Provide 4 examples of non-IgE mediated adverse food reactions

A
  • Proctocolitis
  • Enterocolitis
  • Eosinophilic oesophagitis
  • Food Protein induced enterocolitis syndrome (FPIES)
40
Q

What is proctocolitis?

A

- Proctocolitis is the passage of bright red blood in mucousy stools in otherwise asymptomatic infants.

  • Involves reactions with breastmilk
41
Q

Enterocolitis involves multiply variable GI symptoms. Identify them. Which food is it associated with?

A
  • Symptoms: feed refusal, persistent vomiting, abdominal cramps, loose stools and constipation
  • Associated with milk, eggs, wheat
42
Q

Identify the symptoms involved in eosinophilic oesophagitis. Which food is it associated with?

A
  • Symptoms: oesophageal inflammation and scarring, feeding disorders, reflux symptoms, vomiting, dysphagia
  • Involves milk, eggs, wheat
43
Q

What are the symptoms of Food protein‐induced entero‐ colitis syndrome?

A
  • Profuse vomiting leading to pallor, lethargy and possibly shock
  • Diarrhoea in 25%
44
Q

Who is affected in Food protein‐induced entero‐ colitis syndrome?

Which food is involved?

A
  • Primarily affects infants.
  • Involves milk, soya, rice, wheat, meat
45
Q

The Food allergic march refers to the change in food allergies with increasing age. Illustrate this with reference to:

  • Infancy
  • Childhood
  • Adolescence
A
  • Infancy: milk, eggs, peanuts
  • Early childhood: soya, wheat, tree nuts, fish, kiwi, sesame, shellfish
  • Adolescence: fresh fruit and vegetables
46
Q

Explain the effect of high temperature in milk allergy sufferers

A
  • Casein is more heat resistant than whey
  • Availability & allergenicity is reduced in food matrix
  • 70% milk‐allergics can tolerate baked milk (in wheat)
47
Q

Explain the effect of high temperature in egg white allergy sufferers

A
  • 75% major proteins in egg white are heat labile
  • Well cooked egg is much less allergenic than raw egg
  • 70% of egg‐allergics can tolerate baked egg (in wheat)
48
Q

Explain the effect of high temperature in peanut allergy sufferers

A
  • Allergenicity increases if dry roasted and decreases if boiled/fried
  • Perhaps explains more allergy in Western societies vs Asian
49
Q

Explain the effect of high temperature in fish allergy sufferers

A

Fish protein is very heat stable, but canned tuna and salmon are significantly less allergenic.

50
Q

Explain the effect of high temperature in PFS sufferers

A
  • Apple proteins are exquisitely heat sensitive
  • Patients with PFS can eat processed apple
51
Q

If someone is allergic to cow’s milk, what else could they react to?

A

92% risk they can react to goat’s milk

52
Q

If someone is allergic to a tree nut, what else could they react to?

A

37% risk they can react to other tree nuts (walnut, brazil, cashew, hazelnuts)

53
Q

If someone is allergic to a fish, what else could they react to?

A

50% risk they can react to other fish (salmon, swordfish and sole)

54
Q

If someone is allergic to a shellfish, what else could they react to?

A

75% risk they can react to other shellfish (crab, lobster, shrimp)

55
Q

If someone is allergic to pollen, what else could they react to?

A

55% risk they can react to fruits or vegetables

56
Q

Identify the 4 steps involved in diagnosing a food allergy

A
  • Medical history
  • Physical examination
  • Screening tests
  • Diagnosis verification
57
Q

Which 3 things should one gather when taking a medical history for a potential food allergy?

A
  • Context of reaction
  • Presenting symptoms
  • Food considerations
58
Q

On a physical examination for a potential food allergy, what two things should be done?

A
  • Identify manifestations of food allergy
  • Differential diagnosis with other allergic conditions e.g. eczema
59
Q

Identify and describe some IgE-mediated screening tests

A
  • Serum specific IgE: IgE circulating in blood
  • Skin prick tests: response of skin mast cells to allergens
60
Q

Which investigation can one perform for both IgE-mediated and non IgE-mediated food allergy?

A

Elimination diet

61
Q

How can one verify a diagnosis of a potential food allergy?

A

Controlled oral food challenges

62
Q

What should one ask about context of a reaction in a medical history for a food allergy?

A
  • Age of onset.
  • List of all suspected foods causing symptoms
  • Route of exposure (ingestion, skin contact, inhalation).
  • Activity at time of exposure (exercise/alcohol)
63
Q

What should one ask about a patient’s symptoms in a medical history for food allergy?

A
  • Severity, timing and duration of symptoms
  • Symptom onset after food exposure.
  • Treatment provided and response
64
Q

What should one consider about food when taking a medical history for a food allergy?

A
  • Food preparation (cooked, raw, added ingredients)
  • Minimal quantity of food exposure required to cause symptoms
65
Q

Outline the 3 steps involved in an immunoassay for detection of specific IgE

A
  • Allergen is absorbed and immobilised to a solid phase.
  • Patient’s serum is added followed by incubation
  • Allergen‐bound IgE is detected by an enzymatically labeled anti‐human IgE monoclonal antibody
66
Q

What are the most commonly used techniques for immunoassays for IgE antibodies?

A
  • ELISA‐Plates
  • Western blots
  • Microarrays
67
Q

Identify three steps in active management of food allergies

A
  • Anticipatory allergy testing
  • Dietetic advice for dietary exclusions
  • Prescription of emergency medication
68
Q

What are the 2 steps involved in anticipatory allergy testing?

A
  • Test for cross‐reactive allergens to minimise dietary exclusions.
  • Test for known potential future food allergens i.e. peanut in egg allergy
69
Q

Explain how re-introduction and desensitisation can also be used in the active management of food allergies

A
  • Re‐introduction of foods where allergy known to resolve
  • Desensitisation to food allergens e.g. use baked milk or baked egg in re‐introductions
70
Q

How are skin prick tests and serum IgE blood tests used?

A
  • Determine presence of sensitivity not allergy
  • Level of sIgE / size of SPT correlates with likelihood of allergy and not severity

MK - (LUSUMA) Immune System (4 decks)

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