Food allergy/intolerance Flashcards
What is somatosensation disorder?
Hisotry similar to that of allergy but psychological rather than pathological cause
Can cause restrcitive/unhealthy eating
What does the skin sensitisation theory of allergy suggest about what the two main contributors to developing a food allergy are?
Break in infants skin - eczema/skin infection allows allergens from environment into skin - react with immune system
Child does not have contact form GI tract and absence of GI exposure to the allergen
What is the skin sensitisation theory of allergy?
Allergens enter through skin recofnised as foreign and harmful -> sensitised. When encountered again -> full immune repsonse (allergic reaction)
What can help prevent allergies from developing?
Regular GI tract exposure
Preventing allergens entering through skin barrier
When do babies start to be weaned?
6 months
What criteria is used to classify allergies?
Cooms-Gell classification
What antibodies are ass with type I allergic reaction?
IgE
How does type 1 hypersensitivity reaction cause an allergic reaction?
IgE -> mast cells and basophils release histamines and cytokines
What allergic reaction causes an immediate reaction to food eg anaphylaxis?
Type I
What happens in a type 2 hypersensitivity reaction?
IgG and IgM antibodies react to allergen -> complement system
What type of hypersensitivity reaction causes haemolytic disease of the newborn and transusion reactions?
Type 2 - complement system, IgG, IgM
What type of hypersensitivity reaction causes SLE, rheumatoid arithritis and Henoch-Schonlein pupura?
Type 3 - immune complexes accumulate and cause damage to local tissues
What type of hypersensitivity reaction causes organ transplant rekection and contact dermatitis?
Type 4 - cell mediated T lymphocytes
What conditions are Type 3 HS reactions ass with>
Autoimmune
How does type 4 HS reaction cause rejection?
Innapropriate activation of T cells -> inflamamtion and damage to local tissues
What are important areas to cover in an allergen history>
Timing after exposure to allergen
Previous and subsequent exposure and reaction to allergen
Symptoms of rash, swelling, breathing difficulty, wheeze and cough
Prev personal and FH of atopic conditions and allergies
Three ways to investigate allergy
Skin prick testing
RAST testing - IgE
Food challenge
What do skin testing and RAST actually assess?
Sensitisation NOT allergy
Whatis gold standard for diagnosing food allergy and why?
Food challenge
Measures IgE therefore actual allergic reaction not just sensitisation
What controls are used with antigen in skin prick testing?
Water and histamine dots also placed on skin
How get infor from skin prick test?
Size of wheels after 15 minutes
How get infor from skin prick test?
Size of wheels after 15 minutes
What condition is patch testing most helpful in?
Allergic contact dermatitis in response to specific allergne
NOT food allergies
Assess after 2-3 days
Why can RAST testing not be used for allergen specific testing in atopic condtiions?
Results come back positive for everything test
What does RAST measure?
Total and allergen specific IgE quantities in blood
What is important about how conduct food challenge?
In specialised unit with very close monitoring
Management of food allergies
Establish correct allergen essential
Avoidance of that allergen and foods that trigger reactions
Prophylactic antihistamines if exposure inevitable
Adrenalin autoinjector if at risk of anaphylaxis
What is immunotherapy?
Lengthy process gradually exposing patients to allergens over months - aim of reducing reaction to certain foods or allergnes
What do you treat people with after exposure? (non anaphylaxis)
Antihistmaines eg cetirizine
Steorids eg oral prednisolone, topical hydrocortisone or IV hydrocortisone
What age group is affected by cows milk protein allergy?
Children under 3 years
How long does it take for an IgE mediated vs non-IgE mediated reaction to cows milk to occur?
IgE - rapid reaction, occurs within 2 hours
non-IgE - slowly over several days
Lactose intolerance vs cows milk intolerance vs cows milk allergy
Lactose intolerance - intolerance to the sugar lactose in milk
Cows milk intolerance - same GI symptoms as allergy, no allergic sy,ptoms
Cows milk allergy - allergic to proteins in cows milk
Which babies is cows milk allergy more likely in?
Formula fed
Personal or family hisotry of other atopic conditions
When does cows milk allergy present?
Under 1 years
GI problem
- Bloating and wind
- Abdominal pain
- Diarrhoea
- Constipation
- Vomiting (effortless)
- Blood or mucus in stool
- Colicky/irritable
- Feed refusal
Allergic symptoms in response to cows milk protein
Urticarial rash (hives)
Angio-oedema - facial swelling
Cough or wheeze
Sneezing
Watery eyes
Eczema
How to diagnose cows milk allergy?
Full history and exam
Skin prick testing to support but not always necessary
Management of cows milk allergy
Breast feeding mothers avoid dairy products
Replace forumla with hydrolysed formulas
Severe - elemental formulas of base aas eg neocate
How often should a child be tried on the first step of the milk ladder?
Every 6 months after one year old
