Allergy: Food Allergy And Intolerance Flashcards by Kirsty Sutherland

Define food allergy

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

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Define food intolerance

Numerous adverse responses to foods that do not involve an immune response

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Are food allergies more common in children or adults?

Children - 6%

Adults - 1 to 2%

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Non immune mediated/primary food intolerances are classified into…

Food characteristics:

reaction to pharmacologically active food components e.g caffeine
illness in response to toxins from microbial contamination or to scromboid fish toxin

Host characteristics:

metabolic disorders e.g lactose intolerance
Psychological or neurological responses such as food aversion or rhinorrhoea caused by spicy foods

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A scromboid fish toxin reaction involves…

A reaction that results from eating spoiled oily fish e.g tuna or mackerel where excess histamine produced, from fish decay, produces symptom similar to allergy

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Immune mediated (food allergy and coeliac disease) are classified into…

IgE mediated and non-IgE mediated reactions

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What IgE mediated food reactions are there?

Acute urticaria/angioedema
Anaphylaxis
Pollen-food syndrome PFS
Food associated exercise induced anaphylaxis

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What non IgE mediated food allergy reactions are there?

Proctocolitis
Enterocolitis
Eosinophilic oesophagitis
Food protein induced enterocolitis syndrome (FPIES)

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Are food allergies usually IgE mediated?

Yes

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Describe the symptom onset of IgE mediated food allergies

Immediate 5-30 minutes

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What common foods cause IgE mediated allergy?

Milk and eggs
Peanuts and tree nuts
Fish and shellfish
Fruit and vegetables (PFS)

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What is the presenting age of IgE mediated allergy?

Variable - age of contact
All milk allergies by 1
PFS in adolescence

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Can milk and egg allergy resolve?

Yes

Others persist into adulthood

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Describe the symptom onset of non IgE mediated food allergies

Delayed - hours to days

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What common foods can cause non IgE mediated allergy?

Milk and soya
Wheat
Rice, oats (FPIES)

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What is the presenting age of non IgE mediated food allergy?

Infancy and early childhood

All milk allergy by 1

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Does non IgE mediated reactions resolve earlier or later than IgE mediated?

Earlier

Many resolve by school age

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What skin presentations can occur with IgE mediated food allergies?

Pruritus
Erythema
Acute urticaria - localised or generalised
Acute angioedema - most commonly lips, face, around eyes

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What GI symptoms can occur with IgE mediated food allergies?

Angioedema of lips, tongue and palate
Oral pruritus
Nausea
Vomiting
Diarrhoea
Colicky abdominal pain

What respiratory symptoms can occur with IgE mediated food allergies?

Upper respiratory- blocked/runny nose, sneeze, itch

Lower - wheeze, cough, DIB

What cardiovascular symptoms can occur with IgE mediated food allergies?

Rare in food allergy
Pallor
Drowsy
Hypotensive

What skin symptoms can occur with non IgE mediated food allergies?

Pruritus
Eczema
Atopic eczema

What GI symptoms can occur with non IgE mediated food allergies?

GORD
Loose or frequent stools
Blood and/or mucus in stool
Abdominal pain, infantile colic
Food refusal or aversion 
Constipation 
Perianal redness
Faltering growth with at least one or more GI symptoms +/- eczema

Describe the presentation of pollen food syndrome

Pruritus and mild oedema confined to oral cavity (lips, tongue, mouth, throat)
Uncommonly progressing
Associated with hay fever
Raw fruit and vegetables

Describe the presentation of food associated exercise induced anaphylaxis

Food triggers anaphylaxis only if ingestion is followed temporarily (within 2 hours) by exercise Wheat, shellfish, celery

Describe the presentation of urticaria / anaphylaxis caused by IgE mediated food allergy

Acute hives and swelling with GI but not respiratory or CVS symptoms

How does proctocolitis present?

Passage of bright red blood in mucousy stools in otherwise a symptom infants Milk Through breastfeeding

How does enterocolitis present?

Multiple and varying GI symptoms including feed refusal, persistent vomiting, abdominal cramps, loose and frequent stools and constipation Milk Eggs Wheat

How does eosinophilic oesophagitis present?

``` Symptoms from oesophageal inflammation and scarring Reflux symptoms Vomiting Dysphagia Food impaction ``` Milk, eggs, wheat

How does FPIES present?

Profuse vomiting leading to pallor, lethargy and possibly shock Diarrhoea in 25% Milk, soya, rice, wheat, meat

What food allergies typically occur in infancy?

Milk Egg Peanut

What food allergies typically occur in early childhood?

``` Soya Wheat Tree nuts Fish, shellfish Kiwi Sesame ```

What food allergies typically occur in adolescence?

Fresh fruit and vegetables (pollen food syndrome)

Food processing destroys...

Conformational (folded) epitopes | But sequential epitopes preserved

What is cross reactivity?

When the proteins in one substance is found in another, so if you are allergic to one thing, may be allergic to another substance with same protein present

If there is an allergy to cow’s milk, due to cross reactivity, there is a 92% risk of being allergic to...

Goat’s milk

If a child is allergic to a tree nut e.g walnuts, there is a 37% chance of reacting to...

Other tree nuts e.g cashew, Brazil, hazelnuts

If a child is allergic to pollen, there is a 55% chance they will react to...

Fruits/vegetables e.g apple, peach

How is a food allergy diagnosis made?

Clinical history - context of reaction - presenting symptoms - food considerations Physical examination - identify manifestations of allergy - differential diagnosis - other allergic conditions e.g eczema Screening tests - skin prick - measuring specific IgE antibodies in blood - elimination diet Diagnosis verification - controlled oral food challenges

What questions in the history would be important to ask?

Age of onset List of foods suspected of causing symptoms Route of exposure Activity at time of exposure (exercise or alcohol can potentiate reaction) Intercurrent illness Food ingested without symptoms All observed symptoms and severity Timing of symptom onset in relation to food exposure Duration of symptoms Treatment provided and response Manner in which food was prepared - cooked/raw Minimal quantity required to cause symptoms

For IgE mediated food allergy, what is the most helpful confirmatory test?

Skin prick tests and measurement of specific IgE antibody in blood

How is a skin prick test done?

A drop of the allergen placed on the skin, the site is marked, and pricked with a needle. Any weals are measured. - Weals of 4mm or greater are considered positive

Are non IgE mediated food allergies easier or harder to diagnose?

Harder - relies on clinical history and examination

If there is suspicion of non IgE mediated allergy, what diagnostic test can be done?

Endoscopy and intestinal biopsy - diagnosis supported by eosinophilic infiltrates

How are food allergies managed?

Avoidance of relevant food/foods Child and family must be able to manage an attack - written management plan and training Drug for mild reactions (no cardio respiratory symptoms) = non-sedating antihistamines Drug for severe reactions - adrenaline given IM with epipen

What is the gold standard diagnostic test?

Double blind placebo controlled food challenge