Food Allergy By Dr Rowan Brown

Problem Common - ( % 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

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

IgE - mediated allergy FoodAge of onsetResolution Hen’s Egg6-24mths7yr (75%) Cow’s Milk6-12mths5yr (76%) Peanut6-24mths 5yr (20%) Fishchildhoodpersistent Shellfishadulthoodpersistent Wheat6-24mths5yr (80%) Soya6-24mths5yr (70%) KiwiAny Agenot known

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

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

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

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

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

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

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