Food Allergy Flashcards
Define allergic rhinitis/ hay fever
Blocked/ runny nose
Itchy nose
Sneezing
Triggered: pollen, pets, HDM
Define allergic conjunctivitis
Red, swollen, itchy, watery eyes
Can occur with allergic rhinitis
Define asthma
Chest symptoms wheeze/ cough/ shortness breath/ tight chest
Not always allergic
Define atopic dermatitis/ eczema
Commonest chronic inflammatory skin disease
Itch and excoriation
What is urticaria (hives)?
Acute/ chronic (+-6w) macula-popular pruritus rash without or with angioedema
Different categories of insect allergy
Often bee or wasp
Mild - local
Moderate - urticaria
Severe - anaphylaxis
What is allergic conjunctivitis?
Red, swollen, watery, itchy eyes
Compare the prevalence of food allergies in children and adults
Children 6%
Adults 2%
Why is the most common food allergy in infants? When does it present?
Milk
2-3%
Always presents by 12months
Symptoms can present many weeks after first ingested
Two types of presentation of milk allergies
Immediate onset - IgE mediated 40%
Allergy symptoms affecting skin, respiratory and GI tracts
Urticaria, cough, wheeze, vomiting, diarrhoea. Can cause anaphylaxis and be fatal
OR
Delayed onset - non-IgE mediated 60%
Multiple GI symptoms
Difficult to diagnose - younger presentation similar to colic, reflux
14 major food allergens
Celery Cereals contains gluten Crustaceans Eggs Fish Lupin - in flour Milk Molluscs Mustard Nuts Peanuts Sesame seeds Soya Sulphur dioxide (sulphites)
Define allergy
Not a disease but mechanism leading to disease
Immunological hypersensitivity can lead to variety of different diseases via different pathomechanisms with different approaches in diagnosis, therapy, prevention can be IgE mediate dor non-IgE mediated
Define allergen
Any substance stimulating production IgE or a cellular immune response, usually a protein/ can carbohydrate
Hypersensitivity define
Abnormally strong response to a stimulus
Define sensitisation
Production IgE antibodies detected by serum IgE assay or skin prick test after repeated exposure to an allergen
Define atopy
Tendency produce IgE antibodies in response to ordinary exposure to potential allergens
Strongly associated: asthma, rhinitis, eczema and food allergy
Define anaphylaxis
Serious allergic reaction with bronchial, laryngeal and CVS involvement
Rapid onset and can cause death
What is a food?
Substance intended for human consumption including drinks and any substance used manufacture, prep or treatment of food
Food intolerance meaning
Adverse responses to foods doesn’t involve immune response
Food allergy presentation IgE mediated vs non IgE mediated. Symptoms onset, common foods, presenting age, natural history
IgE: immediate 5-30mins, milk/ eggs/ peanuts/ tree nuts/ fish/ shellfish/ fruit/ veg, age of contact, all milk allergies by 1 yr, pFS (f&v) in adolescence, milk/ eggs can resolve, others persist
Non IgE - delayed hrs- days, milk/ soya/ wheat/ rice/ oats, infancy and early childhood, resolve earlier than IgE- many by school age
Symptoms in IgE and non IgE mediated allergies skin
IgE: skin - pruritus, erythema, acute urticaria/
angioedema
Non-IgE: priorities, eczema, atopic eczema
Symptoms in IgE and non IgE mediated allergies GI
IgE- angioedema, oral pruritus, colicky abdo pain
Non IgE: food refusal/ aversion, abdo pain, infantile colic, gastro-oesophageal reflux disease, loose/ frequent stools, blood/ mucus stools, constipation, perianal redness, pallor, tiredness, faltering growth + GI symptoms +/- eczema
Respiratory and CVS symptoms IgE and non IgE
IgE: blocked/ runny nose, sneeze, itch, wheeze, cough, DIB
Pallor, drowsy, hypotension
Non-IgE: none
What is food associated exercise induced anaphylaxis?
Food triggers anaphylaxis only if ingestion if followed temporally within 2hrs by exercise
What is pollen food syndrome?
Pruritus and mild oedema confined to oral cavity uncommonly progressing, associated with hay fever
What is protocolitis
Passage bright red blood in mucous stools in otherwise asymptomatic infants
Milk breastfeeding
What is enterocolitis
Multiple/ varying GI symptoms include feed refusal, persistent vomiting, abdo cramps, loose/ frequent stools, constipation
Milk eggs wheat
What is eosinophilic oesophagitis
Symptoms oesophageal inflammation and scarring of feeding disorders, reflux symptoms, vomiting, dysphagia, food impaction
Milk eggs wheat
What is food protein induced enterocolitis
Primary infants
Profuse vomiting leading pallor, lethargy, possible shock, diarrhoea
Milk soya rice wheat meat
High food allergies tend to present in infancy, early childhood and adolescence?
Infancy - milk, eggs, peanuts
Early childhood - soya, wheat, tree nuts, fish, shellfish, kiwi, sesame
Adolescence - fresh fruit and veg
How can temperature and food matrix effect allergies? Why?
Heating, baking, boiling, canning
Can reduce allergens in some ppl, e.g. 70% milk allergic can tolerate baked milk, same with egg
Food processing destroys conformational (folded) epitopes
Give examples of cross- reactive food allergens
Cows milk - 92% react goats milk
Tree nut - 37% react other tree nuts
Fish - 50%
Shellfish - 75%
Pollen - 55% react fruit and veg
Steps of evaluating a child with possible food allergy
Medical history - context, symptoms, food considerations
Physical exam - manifestations, deferential diagnosis, other allergic conditions
Screening test - IgE mediated FA: skin prick, blood specific IgE. IgE and non: elimination diet
Diagnosis verification - controlled oral food challenges
Essential elements of a medical history in suspected food allergy
Age of onset List of all foods suspected Route of exposure Activity at time (exercise/ alcohol) Intercurrent illness (mimic) List of foods previously ingested without symptoms All symptoms & severity Timing symptoms Duration Treatment provided Manner food prepared Minimal quantity of food required to cause symptoms
How is a typical immunoassay for detection to specific IgE carried out?
Allergen absorbed and immobilised to solid phase
Patients serum added -> incubation 30-60mins -> washing steps -> allergen bound IgE detected by enzymatically labelled anti-human IgE monoclonal antibody
Most commonly used: ELISA-plates, western blots, strips, immunoCAP, microarrays
How can you detect IgE?
Serum specific IgE - circulating in blood
OR
Skin prick tests - response mast cells
Determine presence of sensitivity
Level of sIgE/ size SPT correlates with likelihood of allergy (positive predictive thresholds developed for common allergens)
