FOOD INTOLERANCE It caused by factors inherent in food ingested: Enzyme Deficiency GI disorders Anatomical defect Physiological effects of Active Substances Food Additives & Contaminants Neurologic disorder
FOOD ALLERGY An adverse health effect arising from a specific immune that occurs on exposure to a given food
EPIDEMIOLOGY OF FOOD ALLERGY Food allergy is on the increase in developed countries Factors contributing to the epidemic appear to be related to the modern lifestyle but as yet are poorly understood. The incidence of food allergy-related anaphylaxis, the most severe consequence of food allergy, is rising particularly in the under 4-year age group. Overall more than 90% of food allergies in children are caused by cow’s milk, hen’s egg, soybean, wheat, peanut, tree nut, fish, and shellfish. → overall 8% In adults sea food( 2.3%), peanut& tree nut(1.2%) → overall 3.5-4 %
FREQUENTLY ALLERGENIC FOODS Most common food allergies in young children: Milk (casein, whey) Eggs Wheat (gluten) Soy Peanuts Tree nuts Shellfish Most common food allergies in older children & adults Fish Shellfish Peanuts Tree nuts
PATHOPHYSIOLOGIC MECHANISMS OF FOOD ALLERGY In the susceptible host, a failure to develop or a breakdown in oral tolerance, commonly a result of heavy occupational exposure or sensitization to cross- reactive allergens may result allergic response IgE mediated Non IgE mediated Mixed IgE & non IgE mediated
Immediate <1 hour Delayed >24 hours Volume required for reaction Class IgE mediatedNon-IgE mediated Time to onset of reaction Immediate <1 hour Delayed >24 hours Volume required for reaction Small (e.g. <10 ml)Large (e.g. >100 ml) Symptoms/ syndromes Urticaria, angioedema, vomiting, anaphylaxis, oral allergy syndrome, eczema Diarrhoea, eczema, failure to thrive, gastrooesophageal Reflux,food proteininduced enteropathy, enterocolitis and proctocolitis, multiple food allergy Diagnostic procedures Above signs or symptoms by history or oral food challenge AND positive IgE antibodies (skin prick test or cap-FEIA) Home based elimination and Rechallenge sequence (no risk of anaphylaxis
HISTORY &PHYSICAL EXAMINATION Food presumed to have provoked the reaction Quantity of the suspected food ingested Length of time between ingestion &development of symptoms Whether similar symptoms developed on other occasions when the food was eaten Whether other factors (exercise, alcohol, drugs) are necessary How long since the last reaction to food occurred Personal hx of atopy Family hx of food allergy & atopy Diet diaries
SKIN PRICK TEST Skin prick or puncture tests to foods are very useful when properly performed and interpreted. Negative prick/puncture skin tests have a high negative predictive accuracy for many foods (>95% for the common foods). Positive prick/puncture skin tests have a high positive predictive accuracy for egg, milk and peanut in young children, and the size of the skin test is relatively predictive. A negative test with a suspicious history requires a food challenge before the food is returned to the diet
INVITRO TEST FOR SPECIFIC IGE Food specific IgE exceeding the diagnostic values indicate that patients are more than 95% likely to experience allergic reaction after ingestion of specific food PREFERENCE FOR IN VITRO TESTS VS SKIN TESTS Patients with extensive dermographia Patients with extensive atopic dermatitis or generalized urticaria Patients who cannot discontinue antihistamines Areas where there are no allergists to perform skin testing
ORAL FOOD CHALLENGE PROCEDURES Oral food challenges (particularly double-blind placebo-controlled food challenge) represent the accepted gold standard investigation for objective diagnosis of both immediate and delayed-onset food allergy. Oral food challenges are clinically indicated to demonstrate allergy or tolerance to achieve safe dietary expansion or appropriate allergen avoidance
20 CHALLENGE Double-blind Placebo-controlled Food Challenge (DBPCFC) Freeze-dried food is disguised in gelatin capsules Identical gelatin capsules contain a placebo (glucose powder) Neither the patient nor the supervisor knows the identity of the contents of the capsules Positive test is when the food triggers symptoms when the placebo does not
21 CHALLENGE CONTINUED Single Blind Food Challenge Supervisor knows the identity of the food Food is disguised in strong-flavoured food e.g. apple sauce; lentil soup Open Food Challenge Sequential incremental doe challenge (SIDC) Determines sensitivity and dose tolerated for each eliminated food in its purest form
INDICATION FOR OFC IndicationRationale Demonstrate tolerance 1. Allergy suspected to have been outgrown, e.g. the child who was previously egg allergic but now returns ever-decreasing allergy test results. 2. When the food has been tolerated in some presentations but not others e.g. baked egg in cakes tolerated but scrambled egg causes a reaction. 3. When allergy tests suggest tolerance, but food never eaten and patient and/or parent too cautious to introduce at home. 4. Cross-reactivity suspected, e.g. the child with a low positive IgE result to wheat but high positive grass pollen sensitization. 5. When the diet is restricted due to a suspicion that one or more foods is resulting in delayed allergic symptoms, e.g. eczema, gastroesophageal reflux. 6. To establish a tolerance threshold to allergen proteins (currently restricted to the research setting). 7. When multiple dietary restrictions are maintained but symptoms are subjective. Demonstrate allergy 1.Suspected food allergic reaction but cause uncertain despite SPT and Sp-IgE testing, 2. Suspected food allergic reaction but equivocal or inconsistent symptoms following consumption of a particular food Monitor therapy for food allergy To monitor response to immunomodulatory treatment in the research setting.
INDICATIVE OF IGE MEDIATED Skin prick test, and or food specific IgE Negative Reintroduction of food into diet; If convincing history of anaphylaxis consider OFC Positive Convincing h/o allergic reaction NO Consider OFC and reintroduction of food YES Strict dietary food avoidance; nutritional support Periodic reassessment; if specific IgE is detectable, reintroduction should be done as OFC
INDICATIVE OF CELL MEDIATED OR MIXED MECHANISM Biopsy, Serologic test for Celiac, Peripheral Eosinophil,,Stool for occult Blood, Hb, Albumin, Total protein Consider skin prick test or Specific IgE Trial of Elimination Diet, foods selected based on experience &result of screening test; if food specific IgE is detectable OFC may be done for reintroduction Resolution NO Review diet & reconsider food. Correct diagnosis? Yes Strict die t
Should be prescribed based on confirmed diagnosis Some times strict avoidance in not necessary -extensively heated product for egg or milk allergy - maternal ingestion of allergen while breast feeding - raw fruit & vegetables causing oral symptoms Labeling of manufactured product Cross contact
EXAMPLES OF FOOD ALLERGENS IN UNEXPECTED AND NONFOOD ITEMS Cosmetics almond or milk in shampoos or ointments Pet food milk, egg, fish, soy Medications lactose in DPI or tablet, soy lecithin Vaccines egg(influenza, yellow fever), milk(DPT) Nutrition supplements glucosamine chondrotin supplements(shark cartilage or shrimp shell) Saliva(kissing) residual protein from meals Transfusion containing allergen from donor ingestion
NATURAL HISTORY OF FOOD ALLERGY Most young children outgrow their food sensitivity within a few years except in most cases of peanut, tree, and seafood
Milk Allergy : most of them become tolerant till 3y/o, 50% by 1y/o, 70% by 2 y/o, 85% by 3 y/o Egg Allergy : 66% become tolerant by 5 y/o Peanut Allergy: 20% become tolerant with age Tree nut Allergy : 9% become tolerant with age
EMERGENCIY MANAGMENT Prompt recognition of reaction Treatment with epinephrine and antihistamines Emergency plans and special considerations for schools
CHANGES IN NOTIONS ABOUT ALLERGY PREVENTION THROUGH DIET Prior notion/recommendation for those at risk for atopy Recent notion Avoid peanut during pregnancyNo proof of effectiveness Avoid food allergens during lactationPossible reduction in eczema, no evidence regarding food allergy Exclusive breast feeding for 3-4 monthsMay protect for atopy, but evidence is modest, lack of evidence for food allergy prevention Alternative hypoallergenic formulaMay protect for atopy, but evidence is modest, lack of evidence for food allergy prevention Delay complementary foods until 4-6 monthsLack of evidence to prevent atopic disease Avoid allergens: milk to 1y/o, egg to 2y/o, and peanut, nut, and fish to 3 y/o Early introduction of allergenic foods at 4-6 m/o may protect against development of food allergy, but firm evidence is lacking
FUTURE THERAPEUTIC STRATEGIES Strict avoidance of allergens is not curative and leaves patients at risk for accidental exposure. As such, several new therapeutic approaches are being tested in clinical trials.
ALLERGEN NON SPECIFIC THERAPIES Humanized monoclonal anti- IgE Traditional Chinese Medicine Probiotics &Prebiotics
SUMMARY Current therapy for food allergy requires education about avoidance in a variety of setting & instruction on when &how to treat inevitable allergic reactions Current therapeutic strategies are focused on harnessing oral tolerance to modulate allergic response using Ag-specific & non specific approaches.