2.1. Food Allergy - Assesment And Diagnosis Flashcards
What is an allergy?
A mechanism leading to disease
Immunological hypersensitivity that can lead to a variety of different diseases via pathomechanisms with different approaches in diagnosis, therapy and prevention
What is the difference between hypersensitivity and allergy?
Hypersensitivity = abnormally strong response to stimulus
Allergy = hypersensitivity reaction initiated but specific immunological mechanisms
What is atopy?
A tendency to produce IgE antibodies in response to ordinary exposure to potential allergens.
Strongly associated with asthma,G rhinitis (hay fever), eczema and food allergy.
What is uritcaria?
Urticaria, also known as hives, is an outbreak of swollen, pale red bumps or plaques (wheals) on the skin that appear suddenly – either as a result of the body’s reaction to certain allergens, or for unknown reasons.
Hives usually cause itching, but may also burn or sting.
What is a milk allergy ? How could someone present with one?
Commonest food allergy in infants
Presents by 12 months of age
Symptoms can present many weeks after first ingested
Presentation:
Can be immediate onset IgE mediated
- typical allergy symptoms affecting skin, resp tract and Gi
- symptoms of urticaria, cough, wheeze, vomit and diarrhoea
- can cause anaphylaxis
Delayed onset non IgE mediated
- multiple GI symptoms
- present similar to colic, reflux
Name 5 major allergens
Celery Cereals with gluten Milk Fish Crustaceans
What is a food allergy?
An adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a food.
Can be IgE (immediate) or non IgE (delayed)
What symptoms would you see with a non IgE mediated response?
Proctocolitis - bright red blood in mucous stools in asymptomatic infants
Eosinophilic oesophagitis - inflammation and scarring
Food protein induced enterocolitis syndrome from profuse vomiting
Enterocolitis GI problems could include - food refusal - constipation - perineal redness - pallor and tiredness - loose or frequent stills
Delayed onset of symptoms and would present in infancy and early childhood
Resolve earlier than IgE
What symptoms would you see in an IgE mediated reaction?
Acute urticaria/angioedema
Upper resp - blocked/runny nose sneeze, itch
Lower resp - wheeze, cough
Anaphylaxis - nut,fish,shellfish, milk, eggs
Pollen food syndrome (pruritis and mild oedema) confined to the oral cavity, associated with hay fever
Food associated exercise induced anaphylaxis (only if ingested food is followed within 2 hrs by excersise)
Immediate onset (5-30mins), variable age of onset dependant on contact (e.g fish and shellfish, peanuts and tree nuts)
Milk and egg allergy can resolve but others will persist into adulthood
How do you test for an IgE mediated food allergy?
Skin prick test
Blood specific IgE - similar to ELISA test principle
How do you screen for an IgE and non IgE food Allergy?
Elimination diet
how would you do an immunoassay to detect antigen specific IgE?
allergen is absorbed and immobilised to a solid phase
patients serum is added followed by incubation for 30-60mins
allergen bound IgE is detected by an enzymatically labeled anti-human IgE monoclonal antibody
focused testing so will get true positive and negative
