Food Allergy Flashcards
Allergen
Substance that stimulates the production of IgE or a cellular immune response
Hypersensitivity
Inappropriate or excessive response to a stimulus
Sensitisation
Production of IgE antibodies after exposure to an allergen
Atopy
Tendency to produce IgE antibodies in response to ordinary exposure to potential allergens
Associated with:
- asthma
- rhinitis
- eczema
- food allergy
Presentation of allergy
Allergic rhinitis: triggered by pets, house dust mites and pollen
- blocked or runny nose
- itchy nose
- sneezing
Allergic conjunctivitis
- red, swollen, itchy and watery eyes
Asthma
- wheeze
- cough
- SOB
- tight chest
Atopic dermatitis (eczema)
- chronic inflammatory skin disease
- itch and excoriation
Urticaria (hives)
- maculo - papular pruritic rash
- +/- angioedema
Insect allergy
Mild - local itchyness, erythema
Moderate - urticaria
Severe - anaphylaxis
Allergies as one ages
Rhinitis prevalence increases with age
Asthma, eczema and food allergy decreases with age
Milk allergy
Presents before 1 years old
Symptoms can present many weeks after exposure
Types of presentation
IgE mediated (40%)
- immediate onset
- affects skin, GI and resp tract
- urticaria, cough wheeze, vomiting and diarrhoea
- can cause anaphylaxis
Non IgE mediated (60%)
- delayed onset
- FPIES - food protein induced enterocolitis syndrome
- predominately multiple GI symptoms
- resolves earlier
Why is non IgE mediated allergy harder to diagnoses
Seen in younger patients - infancy and early childhood
Similar presentation to reflux and colic diseases
Common symptoms of food induced anaphylaxis
Coughing and scratching at throat
Malar flush
REPEATED vomiting
Generalise urticaria
Common food allergens
Celery Crustaceans Eggs Fish Lupin - in flour Milk Molluscs Mustard Nuts Sesame seeds Soya sulphites - beer
Non immune mediated food intolerance
Metabolic e.g lactose intolerance
Psychological - food aversion
Toxic - scromboid dish toxin in fish that is not kept cold
Food associated exercise induced anaphylaxis
Food triggers anaphylaxis only when exercise is done after within 2 hours
Pollen food syndrome
Pollen in fruit can cause pruritis and mild oedema confined to the oral cavity
Rarely progresses
Associated with hay fever, raw fruit and veg
Proctocolitis
- inflammation of rectum and colon
- passage of bright red blood in mucous stool in otherwise asymptomatic infants
- due to milk allergy whilst breastfeeding
Eosinophilic oesophagitis
Oesophageal inflammation and scarring of feeding disorders
- reflux
- vomiting
- dysphasia
- food impaction
Food Preston induce enterocolitis syndrome
Primarily affects infants Profuse vomiting: - pallor - lethargy - possible shock - diarrhoea
- looks like sepsis but markers are abscent
Change in food allergies
Infancy:
- milk
- egg
- peanuts
Early childhood:
- soya
- Wheat
- tree nuts
- fish
- kiwi
- sesame
Adolescence
- fresh fruit
- vegetables
Casein
Protein in milk that is more heat resistant than whey
Whey forms bonds in food - reduces availability and allergenicity
Therefore tolerated baked milk
Allergenicity of peanuts
Increases if dry roasted
Decreases if boiled or fried
Cross reactive food allergens
CSF allergic to cows milk 92% likely to be allergic to goats milk
Tree nuts and other tree nuts - 37%
Fish and other fish - 50%
Shellfish - 75%
Pollen and fruits - 55%
Food allergy diagnosis
Medical history:
- context of reaction
- symptoms - timing, duration and severity
- food considerations - how food is prepared
- route of exposure
- age of onset
- activity at time of exposure - e.g. alcohol
Physical examination
Screening tests:
- skin prick tests
- blood specific IgE
- elimination diet
Diagnosis verification: food challenges
Immunoassay to detect allergen specific IgE
Allergen bound IgE is detected by an enzymatically labelled anti human- IgE monoclonal antibody
Skin prick test
- Determines sensitisation
- size of skin prick test correlates with likelihood of allergy but not severity
Management of food allergy
Identify food causing symptoms
Dietary advice:
- exclusions
- inclusions
- label reading
- food reintroductions
Medical advice:
- emergency management of anaphylaxis - epipen
- allergy to food - antihistamine
Management of milk allergy
Replacement infant formulas:
- extensive hydrolysed formula
- soya - more than 6 months old
- amino-acid formula
- dairy free weaning advice followed by reintroduction
Milk reintroduction
Stage 1 - small crumb of biscuit then to whole biscuit in 5 weeks
Stage 2 - bakes products containing calein milk products
Stage 3 - products containing cooked cheeses or whole cow’s milk
Stage 4 - uncooked cheese, non yoghurt desserts like ice cream
