Allergy: Food Allergy And Intolerance Flashcards
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.
Define food intolerance
Numerous adverse responses to foods that do not involve an immune response
Are food allergies more common in children or adults?
Children - 6%
Adults - 1 to 2%
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
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
Immune mediated (food allergy and coeliac disease) are classified into…
IgE mediated and non-IgE mediated reactions
What IgE mediated food reactions are there?
Acute urticaria/angioedema
Anaphylaxis
Pollen-food syndrome PFS
Food associated exercise induced anaphylaxis
What non IgE mediated food allergy reactions are there?
Proctocolitis
Enterocolitis
Eosinophilic oesophagitis
Food protein induced enterocolitis syndrome (FPIES)
Are food allergies usually IgE mediated?
Yes
Describe the symptom onset of IgE mediated food allergies
Immediate 5-30 minutes
What common foods cause IgE mediated allergy?
Milk and eggs
Peanuts and tree nuts
Fish and shellfish
Fruit and vegetables (PFS)
What is the presenting age of IgE mediated allergy?
Variable - age of contact
All milk allergies by 1
PFS in adolescence
Can milk and egg allergy resolve?
Yes
Others persist into adulthood
Describe the symptom onset of non IgE mediated food allergies
Delayed - hours to days
What common foods can cause non IgE mediated allergy?
Milk and soya
Wheat
Rice, oats (FPIES)
What is the presenting age of non IgE mediated food allergy?
Infancy and early childhood
All milk allergy by 1
Does non IgE mediated reactions resolve earlier or later than IgE mediated?
Earlier
Many resolve by school age
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
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
