APPROACH TO FOOD ALLERGY IN CHILDREN DR MEERA THALAYASINGAM INTERNATIONAL MEDICAL UNIVERSITY RAMSAY SIME DARBY HEALTHCARE MALAYSIA APAPARI WORKSHOP PHNOM PENH CAMBODIA_ 12 TH SEPT 2015 WHY TALK ABOUT FOOD ALLERGY? 1. Difficult problem group of diseases 2. A lot of non-scientific data opinions beliefs stories. 3. Confusion over food allergy, food intolerance, food aversion 4. Too many diseases blamed on allergy too many children are labeled as being food-allergic? DISEASES BLAMED ON FOOD ALLERGY Hyperactivity disorders Autism spectrum disorder Depression Serous otitis media Rhinitis Infantile colic Chronic fatigue syndrome ADVERSE REACTIONS TO FOOD OVERVIEW Food Intolerance (most common) Enzyme deficiency (lactose intolerance) Toxic effect (bacterial contamination, food additives) Pharmacological property of the food eg Histamine release Food Allergy (hypersensitivity) Food Aversion (phobia) What is Food Allergy? How Common is Food Allergy? Clinical Symptoms and Classification of Food Allergy Co existing conditions with Food Allergy Approach to Diagnosis and Management
History of symptoms on exposure Diagnosis of IgE food allergy = + Detection of allergic antibody IgE + OFC FOOD ALLERGY DEFINITION CHANGING ALLERGY PATTERNS IN THE LAST 20 YEARS Sensitisation- presence of allergen specific IgE in vitro (blood test) or in vivo test ( skin test) Allergy=attributable symptom AND positive sige Positive skin/serum tests DO NOT necessarily indicate allergy Eg a very large % of peanut sensitised individuals are not actually allergic Not all individuals ordering these tests understand their limitations Not enough challenges are being done to determine the validity of a diagnosis
WHAT ARE THE COMMON TYPES OF FOOD CAUSING ALLERGY? Children Cow s milk Egg Peanut Fish, shellfish, wheat, tree nuts Adults Peanut Tree nuts Fish Shellfish COMMON FOOD ALLERGENS IN DIFFERENT COUNTRIES FOOD CAUSING SEVERE REACTIONS IN OLDER CHILDREN IN SINGAPORE - USA peanuts - Singapore seafood - Sweden fish - France mustard - Israel sesame Others Chinese Herbs 30% 7% 11% 2% 24% 27% Bird s Nest Crustacean Seafood Milk Egg Goh LM, Allergy 1998 CHANGING FOOD ALLERGY TRENDS IN SINGAPORE NATURAL HISTORY OF FOOD Table 1. Natural History of Food Allergy and Cross-Reactivity between Common Food Allergies. Food Usual Age at Onset Cross-Reactivity Usual Age at Resolution Hen s egg white 6 24 mo Other avian eggs 7 yr (75% of cases resolve)* Cow s milk 6 12 mo Goat s milk, sheep s milk, buffalo milk 5 yr (76% of cases resolve)* Peanuts 6 24 mo Other legumes, peas, lentils; coreactivity with tree nuts Tree nuts 1 7 yr; in adults, onset occurs after cross-reactivity to birch pollen Other tree nuts; coreactivity with peanuts Sesame seeds 6 36 mo None known; coreactivity with peanuts and tree nuts Fish Late childhood and adulthood Other fish (low cross-reactivity with tuna and swordfish) Shellfish Adulthood (in 60% of patients Other shellfish with this allergy) Persistent (20% of cases resolve by 5 yr) Persistent (9% of cases resolve after 5 yr) Persistent (20% of cases resolve by 7 yr) Persistent Persistent Wheat 6 24 mo Other grains containing gluten 5 yr (80% of cases resolve) Soybeans 6 24 mo Other legumes 2 yr (67% of cases resolve) Kiwi Any age Banana, avocado, latex Unknown Apples, carrots, and peaches Late childhood and adulthood Birch pollen, other fruits, nuts Unknown Gideon Lack, M.D, NEJM 2008
EVERY FOOD HAS IT S OWN STORY. CO EXISTING CONDITIONS IN FOOD ALLERGY FOOD AS A TRIGGER IN ECZEMA 35% of children with moderate to severe eczema have a positive challenge to food Sampson HA, Pediatrics 1998 < 10% in all children with eczema, possibly much less in children with mild eczema Barnetson RS, BMJ 2002 FOOD ALLERGY AS A TRIGGER OF ASTHMA & RHINITIS? Food allergy as trigger for asthma and rhinitis is not as common as generally believed It is in fact very rare Food avoidance should NOT be recommended before a proper evaluation Food avoidance may cause food phobia or nutritional deficiencies RESPIRATORY SYMPTOMS IN FOOD ALLERGY Coughing or wheezing as the sole manifestation of food allergy is very rare True food allergies generally involve classical signs and symptoms involving the skin, gastrointestinal and/or respiratory systems Sampson HA, J Allergy Clin Immunol 2004 0.1% of 6672 children had skin prick positive food allergy
WHY REFER TO A PAEDIATRIC ALLERGIST? To UNLABEL To REINTRODUCE what is possible (TOLERANCE) To prevent food phobias To allow growth MEDICAL HISTORY IN A WORKUP FOR FOOD ALLERGIES Table 3. Medical History in a Workup for Food Allergies. Question Possible Significance What is the suspected food Consider whether the allergen is typical for the patient s age and population. allergen? Was the suspected food allergen A proportion of patients have a reaction after inhalation of or contact with the ingested, inhaled, or touched? allergen. Does the patient have an aversion Generally patients dislike and refuse food containing the allergen. to the suspected allergen? How soon after exposure to the suspected food allergen did the symptoms occur? What are the specific symptoms and how severe are they? How long did it take for the symptoms to resolve? How reproducible are the symptoms with previous or subsequent ingestion? Does exercise precipitate the symptoms? IgE-mediated allergic reactions usually occur within 20 minutes after the exposure and certainly within 2 hours after the exposure. If the symptoms are not typical of food allergy, consider a differential diagnosis; if the symptoms are severe, alteration of the emergency management plan may be necessary. The typical time to symptom resolution after reaction to food is 4 12 hours. A patient is unlikely to have a reaction to a food just one time, although reactivity may vary depending on factors such as preparation (e.g., depending on whether the egg is raw or cooked and how much antigen it contains). Exercise that precipitates symptoms may suggest a diagnosis such as food-dependent, exercise-induced anaphylaxis.* Gideon Lack, M.D, NEJM 2008 CLINICAL SYMPTOMS OF FOOD ALLERGY IgE Non-IgE Immediate Intermediate Delayed Anaphylaxis : life threatening reaction FOOD ALLERGY CLASSIFICATION IgE mediated Food Allergy Non- IgE mediated Cutaneous : swelling, hives itch, eczema Respiratory : difficulty breathing hoarse voice Gastro : Vomiting, Diarrhea Skin Prick Testing Serum specific IgE (ssige)/rast Component Resolved Diagnostic? Patch Testing SPT PROCEDURE 1 gently lifting up of the skin 2 COMPARISON ON OF TEST T DEVICES E FOR SPT CARR ET AL JACI 2005 :116: 341-6
Probability of reacting to a food at a specific IgE level Sampson HA J Allergy Clin Immuno 2001:107 891-6 SPT/SSIGE ACCURACY risk IgE reaction HIGH SENSITIVITY AND SPECIFICITY TO PREDICT CHALLENGE OUTCOME 100% 60% False Negatives 5% False Positives 100% 5% False Negatives 60% False Positives? risk IgE reaction risk IgE reaction 40% Sensitivity (True positives) 0% Sensitivity 95% Specificity (True Negatives) Specificity 95% Sensitivity (True Positives) 0% Sensitivity Specificity 40% Specificity (True Negatives) LOW SENSITIVITY, HIGH SPECIFICITY In this case, the positive test means the disease likely (low false positives) A negative test is not very helpful, because sensitivity is low (high false negative) HIGH SENSITIVITY, LOW SPECIFICITY In this case, a negative test means the disease is not likely (low false negatives) A positive test is not very helpful, because specificity is low (high false positives). ALLERGY TESTING SPT fast and easy to do more sensitive NOT PAINFUL can use for fresh foods more false positive cannot be done on abnormal skin no antihistamines sige in serum (RAST) Alternative to skin testing in patients with extensive eczema or dermatographism quantification expensive consider in serious anaphylactic reaction Sensitization Disease Establish food Allergy 1. Via history 2. Via food elimination/challenge
CHALLENGE FOOD - FLUIDS FOOD CHALLENGE Start with 1 drop on the lip 1 ml 4 ml 10 ml 20 ml 20 ml 20 ml 25 ml Total = 100 ml Disadvantages Possibility of a severe reaction Time-consuming Advantages Lessen fear and stress Allows a more varied diet Determination of threshold level Promotes tolerance? CHALLENGE FOOD - SOLIDS Start with a small bit on the lip 1 gm 4 gm 10 gm 20 gm 20 gm 20 gm 25 gm Total = 100 gm INFANT FEEDING AND ALLERGY PREVENTION No restriction on maternal diet Breastfeeding is best Hydrolysed formula Weaning 4 to 6 months No evidence for delaying weaning (even in atopic children) Greer AAP Guidelines, Pediatrics 2008 Boyce, J Allerg Clin Immunol 2010 LEAP Study NEJM 2015 CONVENTIONAL MANAGEMENT STRATEGIES OF FOOD ALLERGY Strict Avoidance of the trigger Identify and confirm Action plan +/- epipen In event of accidental exposure Patient education in re hidden exposures Monitor Adequate nutrition Appropriate alternative ( eg hydrolysed formula) Consider challenge depending on probability of tolerance
WHEN IS IT UNLIKELY TO BE A FOOD ALLERGY? 1. If there are no skin symptoms(esp immediate type) 2. If the child is allergic to unusual foods 3. If the reaction only happens sometimes when the person eats the food look for something else! 4. If the child is labeled allergic to many foods. 5. When claims are made that allergy is responsible for many diseases CONCLUSION True food allergy is uncommon In immediate-type food reactions, the skin is almost always involved In delayed-type food reactions, the gastrointestinal tract is involved It is always important to get a proper diagnosis of food allergy