Allergy Flashcards
Definition of hypersensitivity reaction
Reproducible symptoms/signs following exposure to a defined stimulus at a dose which is tolerated by normal people
Definition of an allergy
Hypersensitivity reaction initiated by immunological mechanisms leading to disease.
IgE or non-IgE mediated
Definitions of atopy
Personal and/or familial tendency to produce IgE antibodies in response to ordinary exposures to potential allergens
Associated with asthma, rhinoconjunctivitis, food allergy and eczema
Causes of food intolerance
Food: pharmacological (tyramine, caffeine), toxin (alcohol)
Host: metabolic (lactose intolerance), psychological
Relevance of mechanisms of allergy exposure
Cutaneous exposure leads to allergy
Oral exposure leads to tolerance
Sensitivity of IgE testing as an allergy screening
Poor sensitivity
Only a proportion of people with IgE positive test have an allergy
Mediators released on mast cell degranulation
Histamine Prostaglandins Tryptase Leukotriene IL5
Action of histamine
Vasodilation
Bronchoconstriction
Mucus hypersecretion
Action of prostaglandins
Bronchoconstriction
Action of IL5
Attacks and primes eosinophils
Action of leukotrienes
Bronchoconstriction
Mucus hypersecretion
Difference in onset and resolution of symptoms with IgE and non-IgE mediated allergy
IgE
- onset within 2 hours of exposure
- resolves within 12 hours
Non-IgE
- onset hours or days post exposure
- resolves after many days
Phenotype examples of non-IgE mediated food allergies
Coeliacs/dermatitis herpetiformis
Food protein induced enteropathy
Food protein induced enterocolitis syndrome
Cows milk protein induced iron deficiency anaemia
Food protein induced proctocolitis
Symptoms of IgE mediated allergy
Acute angioedema Acute urticaria Pruritis Wheeze Stridor N+V Abdo pain Diarrhoea
Symptoms of non-IgE mediated allergy
N+V Diarrhoea Blood in stool GORD Abdo pain Pruritis
