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Food Allergy By Dr Rowan Brown

Food Allergy By Dr Rowan Brown. Problem. Common - (1.6 - 8% of population) Attitude - Medical vs Common Opinion Service Provision - access to specialist opinion + testing Doctor’s Agenda nutritional adequacy of child quality of life parental anxiety.

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Food Allergy By Dr Rowan Brown

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  1. Food AllergyBy Dr Rowan Brown

  2. Problem • Common - (1.6 - 8% of population) • Attitude - Medical vs Common Opinion • ServiceProvision - access to specialist opinion + testing • Doctor’s Agenda • nutritional adequacy of child • quality of life • parental anxiety

  3. Allergic Types • IgE (Type 1 hypersensitivity) • “Classic” Peanut Allergy • Atopy & anaphylaxis (rapid 20mins -2hrs) • non-IgE (IgG) • examples - coeliac disease • non-specific + delayed symptoms • Intolerance • multiple types - common: lactose intolerance

  4. IgE - mediated allergy

  5. IgE - mediated allergy • Presents with multi-system involvement • urticaria, angio-oedema, rhinitis, cough, eczema vomiting, diarrhoea, abdominal pain, • rapid onset • High association with atopy: ⇒ if present indicates higher likelihood of anaphylaxis • Associated with multiple allergies

  6. IgE - Diagnosis • 4 modalities • History (very important) • IgE-specific titres (CAP-RAST) • Skin prick testing (SPT) • Food Challenges • Tests are sensitive, but have poor specificity, however, in conjunction with positive predictive values and post test probabilities a diagnosis can be made in 70% of cases

  7. IgE Allergy Treatment • Treatment entails elimination of food stuffs • Oral challenge (depending upon natural history of allergy and severity of reaction) • Advice about anaphylaxis + treatment of associated atopy (asthma) • legal vs medical assessment for anaphylaxis prophylaxis • If every child with wheeze treated, (IM adrenaline + training/antihistamine/bronchodilator) the cost per life saved calculated at $20,000,000

  8. Non-IgE Allergy • Onset typically delayed (4-48hrs), and thus poor association with precipitants. • IgG testing not specific with poor concordance - all food stuffs will develop an IgG response. Exceptions to this include coeliac disease with tissue transglutaminase having a high specificity • Management with elimination diets + if necessary food challenges (under medical surveillance if reaction severe) • Unclear association with IBS

  9. Intolerance • Not an immune response • Common - Lactose intolerance. • Inability to hydrolyse lactose to monosaccharide • Results in bloating, diarrhoea, abdominal pain -develops several hours after indigestion • Enterases in gut facilitate hydrolysis. May become functionally inactive post-infection or congenitally missing. It is common post rotavirus infection, but not specific to the young

  10. Cow’s Milk Allergy • Presents with an acute IgE and delayed IgG response. • Typically occurs post breast feeding and introduction of milk - 4-6mths • Mild symptoms may be managed with an elimination diet, with eHF (extensively hydrolysed formula) or AAF (amino acid formula) - in severe cases • Challenge at 9-12mths • Breast feeding thought to be protective, though inconclusive evidence: current ongoing trial “LEAP” designed to answer question

  11. References • Wikipedia “Food Allergy” & “Intolerance” • Arch Dis Child 2007;92:902-908Guidelines for the diagnosis and managment of cow’s milk protein allergy in infants. Yvan Vandenplas etal. • N Engl J Med 2008;359:1252-60 Food Allergy. Gideon Lack • Clin & Exp Imm;55:378-386 Clinical Immnology Review Series: An approach to the patient with allergy in childhood. R Sporik et al

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