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
2
Q
Is an allergy a disease?
A
Allergy is not a disease itself, but a mechanism leading to disease.
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
4
Q
Define sensitivity
A
Sensitivity is a normal response to a stimulus.
5
Q
Define hypersensitivity
A
Hypersensitivity is an abnormally strong response to a stimulus.
6
Q
Define sensitisation
A
Sensitisation is the production of IgE antibodies after repeated exposure to an allergen.
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.
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.
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
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.
11
Q
Allergic conjuctivitis can occur with allergic rhinitis. Identify its symptoms
A
Symptoms: red, swollen, itchy, watery eyes.
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
13
Q
What is atopic dermatitis/eczema?
A
Atopic dermatitis is the commonest chronic inflammatory skin disease with itch and excoriation
14
Q
What is urticaria?
A
Urticaria is an acute/chronic (±6w) maculo‐papular pruritic rash with/without angioedema
15
Q
Insect allergy is usually to bee/wasp stings. What are its different forms of presentation?
A
- Mild (local)
- Moderate (urticaria)
- Severe (anaphylaxis)
16
Q
Why is allergy important?
A
- Allergy is common
- Allergy is associated with significant morbidity
- Allergy can be fatal
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
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.
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.
20
Q
Define food intolerance
A
Food intolerance are numerous adverse responses to foods that do not involve an immune response.
21
Q
What are the 3 most common food allergies?
A
- Milk
- Eggs
- Peanuts
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
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
24
Q
What are the two types of immune mediated adverse food reactions?
A
- IgE mediated
- Non‐IgE mediated
25
What are the characteristics of food causing non-immune mediated adverse reactions?
- Pharmacologic *eg. caffeine*
- Toxic *eg. scromboid fish toxin*
26
What are the host characteristics in non-immune mediated adverse food reactions?
- Psychological *eg. food adversion*
- Metabolic *eg. lactose intolerance*
27
For IgE-mediated food reactions, describe the following:
- Symptom onset
- Common foods
- Presenting age
- **Symptom onset:** immediate (5‐30 min)
- **Common foods:** milk, egg, nuts, shellfish
- **Presenting age:** variable, depends on contact
28
Do all IgE-mediated allergies last a lifetime?
- PFS is detected in adolescence and milk allergy by 1st year
- Milk and egg allergies can resolve while others persist into adulthood
29
For non IgE-mediated food reactions, describe the following:
- Symptom onset
- Common foods
- Presenting age
- Natural History
- **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
How can IgE-mediated food allergies present in the skin?
- Pruritus, erythema
- Acute urticaria
- Acute angioedema (lips, face, eyes)
31
How can IgE-mediated food allergies present in the Gastrointestinal system?
- Angioedema (lips, tongue,palate)
- Oral pruritus
- Nausea, vomiting, diarrhoea
32
How can IgE-mediated food allergies present in the respiratory system?
- **Upper resp:** blocked/runny nose, sneeze, itch
- **Lower resp:** wheeze, cough
33
How can IgE-mediated food allergies present in the Cardiovascular system?
- Pallor
- Drowsiness
- Hypotension
34
How can non IgE-mediated food allergies present in the skin?
- Pruritis
- Eczema
- Atopic eczema
35
How can non IgE-mediated food allergies present in the Gastrointestinal system?
- Loose or frequent stools
- Blood and/or mucus in stools
- Abdominal pain
- Food refusal/aversion
- Constipation
36
Identify 4 different presentations of IgE-mediated adverse food reactions
- Acute urticaria/angioedema
- Anaphylaxis
- Pollen‐food syndrome (PFS)
- Food‐associated exercise‐induced anaphylaxis
37
When does Food‐associated exercise induced anaphylaxis occur?
- Food triggers anaphylaxis only if ingestion is followed temporally (within 2 hours) by exercise.
- Involves wheat, shellfish, celery
38
Identify some symptoms of Pollen Food Syndrome.
What is it associated with?
- **Symptoms:** pruritus and mild oedema confined to the oral cavity
- Associated with hay fever (raw fruit and vegetables)
39
Provide 4 examples of non-IgE mediated adverse food reactions
- Proctocolitis
- Enterocolitis
- Eosinophilic oesophagitis
- Food Protein induced enterocolitis syndrome (FPIES)
40
What is proctocolitis?
**- Proctocolitis** is the passage of bright red blood in mucousy stools in otherwise asymptomatic infants.
- Involves reactions with breastmilk
41
Enterocolitis involves multiply variable GI symptoms. Identify them. Which food is it associated with?
- **Symptoms:** feed refusal, persistent vomiting, abdominal cramps, loose stools and constipation
- Associated with milk, eggs, wheat
42
Identify the symptoms involved in eosinophilic oesophagitis. Which food is it associated with?
- **Symptoms**: oesophageal inflammation and scarring, feeding disorders, reflux symptoms, vomiting, dysphagia
- Involves milk, eggs, wheat
43
What are the symptoms of Food protein‐induced entero‐ colitis syndrome?
- Profuse vomiting leading to pallor, lethargy and possibly shock
- Diarrhoea in 25%
44
Who is affected in Food protein‐induced entero‐ colitis syndrome?
Which food is involved?
- Primarily affects infants.
- Involves milk, soya, rice, wheat, meat
45
The Food allergic march refers to the change in food allergies with increasing age. Illustrate this with reference to:
- Infancy
- Childhood
- Adolescence
- **Infancy**: milk, eggs, peanuts
- **Early childhood:** soya, wheat, tree nuts, fish, kiwi, sesame, shellfish
- **Adolescence:** fresh fruit and vegetables
46
Explain the effect of high temperature in milk allergy sufferers
- **Casein** is more heat resistant than **whey**
- Availability & allergenicity is reduced in food matrix
- 70% milk‐allergics can tolerate **baked milk** (in wheat)
47
Explain the effect of high temperature in egg white allergy sufferers
- 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
Explain the effect of high temperature in peanut allergy sufferers
- Allergenicity increases if **dry roasted** and decreases if **boiled/fried**
- Perhaps explains more allergy in Western societies vs Asian
49
Explain the effect of high temperature in fish allergy sufferers
Fish protein is very heat stable, but **canned tuna and salmon** are significantly less allergenic.
50
Explain the effect of high temperature in PFS sufferers
- Apple proteins are exquisitely heat sensitive
- Patients with PFS can eat processed apple
51
If someone is allergic to cow's milk, what else could they react to?
92% risk they can react to goat's milk
52
If someone is allergic to a tree nut, what else could they react to?
37% risk they can react to other tree nuts (walnut, brazil, cashew, hazelnuts)
53
If someone is allergic to a fish, what else could they react to?
50% risk they can react to other fish (salmon, swordfish and sole)
54
If someone is allergic to a shellfish, what else could they react to?
75% risk they can react to other shellfish (crab, lobster, shrimp)
55
If someone is allergic to pollen, what else could they react to?
55% risk they can react to fruits or vegetables
56
Identify the 4 steps involved in diagnosing a food allergy
- Medical history
- Physical examination
- Screening tests
- Diagnosis verification
57
Which 3 things should one gather when taking a medical history for a potential food allergy?
- **Context** of reaction
- Presenting **symptoms**
- **Food** considerations
58
On a physical examination for a potential food allergy, what two things should be done?
- Identify **manifestations** of food allergy
- **Differential diagnosis** with other allergic conditions *e.g. eczema*
59
Identify and describe some IgE-mediated screening tests
- **Serum specific IgE:** IgE circulating in blood
- **Skin prick tests:** response of skin mast cells to allergens
60
Which investigation can one perform for both IgE-mediated and non IgE-mediated food allergy?
Elimination diet
61
How can one verify a diagnosis of a potential food allergy?
Controlled oral food challenges
62
What should one ask about context of a reaction in a medical history for a food allergy?
- 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
What should one ask about a patient's symptoms in a medical history for food allergy?
- **Severity, timing and duration** of symptoms
- **Symptom onset** after food exposure.
- Treatment provided and response
64
What should one consider about food when taking a medical history for a food allergy?
- Food preparation (cooked, raw, added ingredients)
- Minimal quantity of food exposure required to cause symptoms
65
Outline the 3 steps involved in an immunoassay for detection of specific IgE
- **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
What are the most commonly used techniques for immunoassays for IgE antibodies?
- ELISA‐Plates
- Western blots
- Microarrays
67
Identify three steps in active management of food allergies
- Anticipatory **allergy testing**
- Dietetic advice for **dietary exclusions**
- Prescription of **emergency medication**
68
What are the 2 steps involved in anticipatory allergy testing?
- Test for **cross‐reactive allergens** to minimise dietary exclusions.
- Test for **known potential future food allergens** i.e. peanut in egg allergy
69
Explain how re-introduction and desensitisation can also be used in the active management of food allergies
- **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
How are skin prick tests and serum IgE blood tests used?
- Determine presence of **sensitivity** not allergy
- **Level of sIgE / size of SPT** correlates with likelihood of allergy and not severity
