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  • This slide demonstrates cross-reactivity between inhalant allergens and food allergens (generally infrequent and typically allergen – specific)
  • The oral allergy syndrome (OAS) appears to have become more prevalent in the past decade, but this may be due in large part to increased awareness. It is estimated that OAS affects up to 40% of adults with pollen allergy, especially to birch, ragweed and mugwort pollen. OAS is a form of contact allergy that is confined almost exclusively to the oropharynx and rarely affects other target organs. Local IgE-mediated mast cell activation provokes the rapid onset of pruritus, tingling and angioedema of the lips, tongue, palate, and throat: and occasionally a sensation of pruritus in the ears, tightness in the throat, or both. Symptoms are generally short-lived and are most commonly associated with the ingestion of various fresh fruits and vegetables. OAS has also been reported to occur in individuals who are sensitive to house dust mite after ingestion of shell fish.
  • 3
  • 4 The clinical history is paramount in the diagnosis of food allergy. Skin tests and specific IgE levels may provide additional information, especially for decision to performing challenge testing or not.
  • Sporik et al (David Hill’s group) from Australia reported that an allergen SPT of ≥ 3mm was a poor predictor of clinically relevant food allergy. However, they found that stronger positive reactions were highly predictive of clinical reactivity to cow’s milk (≥8mm), egg (≥7mm) and peanut (≥8mm) – these were invariably associated with positive challenge tests for these foods. For a subgroup of younger children (≤ 2years) “100% specificity” was achieved with smaller SPT wheal diameters; 6mm for cow’s milk, 5mm for egg and 4mm for peanut. These lower diameters of SPT with “100% specificity” is consistent with previous observations which demonstrate low intrinsic skin reactivity in this age group
  • Diagnosing IgE-Mediated food hypersensitivity disorder skin tests
  • Sampson and Ho reported that quantification of food-specific IgE provided increased positive predictive accuracies for egg, milk, peanut, and fish hypersensitivity compared with skin prick tests. In individuals with serum food allergen-specific IgE levels in excess of the 95% predictive value may be considered reactive, and the need for an oral food challenge would be obviated. A patient with a food allergen-specific IgE less than the 95% predictive value may be reactive and would require a food challenge to confirm the diagnosis. In addition, recent data suggest that monitoring the allergen-specific IgE values may be useful in predicting when follow-up challenges are likely to be negative (i.e. when patients “outgrow” their food allergies). Based on these data, the patient evaluation may begin with the history, progress to skin testing for the suspected foods, and then provide quantification of the level of serum food-specific IgE to determine the probability that a reaction will occur.

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  • GLORIA Module 6: Food Allergy
  • GLORIA™ is supported by unrestricted educational grants from Sponsored by:
  • Global Resources in Allergy (GLORIA™) Global Resources In Allergy (GLORIA™) is the flagship program of the World Allergy Organization (WAO). Its curriculum educates medical professionals worldwide through regional and national presentations and local training programs. GLORIA modules are created from established guidelines and recommendations to address different aspects of allergy-related patient care.
  • US GLORIA Program In conjunction with the American College of Allergy, Asthma and Immunology (ACAAI), GLORIA is now presented for CME Credit in the US to Regional, State and Local Societies. The GLORIA educational materials are available for download on WAO’s website www.worldallergy.org/gloria
  • World Allergy Organization (WAO) The World Allergy Organization is an international coalition of 77 regional and national allergy and clinical immunology societies.
  • WAO’s Mission WAO’s mission is to be a global resource and advocate in the field of allergy, advancing excellence in clinical care, education, research and training through a world-wide alliance of allergy and clinical immunology societies
  •  
  • Food Allergy A GLORIA TM Module Prof. Cassim Motala University of Cape Town and Red Cross Children's Hospital Cape Town, South Africa Prof. Joaquín Sastre Fundación Jimenez Diaz, Department of Medicine Universidad Autonoma de Madrid Madrid, Spain Dr. M. Dolores Ibáñez Hospital Nino Jesus Madrid, Spain Authors Reviewer Prof. Alessandro Fiocchi Melloni University Hospital Milan, Italy
  • Learning objectives
    • At the end of this presentation you will be able to:
    • Recognise the main pathogenic food allergens in adults and children
    • Differentiate between IgE-mediated, cell-mediated and mixed IgE- and cell-mediated food-related diseases in different organ systems
    • Discuss the diagnosis of food allergy and the limitations of diagnostic techniques
    • Review the treatment of food allergy
  • Adverse reactions to food: Definition
    • Any abnormal clinical response attributed to ingestion, contact or inhalation of any food, a food derivative or a food additive
    • Toxic
    • Non toxic or hypersensitivity
  • TOXIC Nontoxic Allergy Intolerance Immune-mediated Non-immune mediated Enzymatic Pharmacologic Undefined Non-IgE-mediated IgE-mediated Adverse Reactions to Food: Position Paper. Allergy 1995; 50:623-635 Adverse reactions to food
    • Precise prevalence is unknown, but estimates are:
    • Adults: 1.4% - 2.4%
    • Children < 3 years: ~ 6%
    • Atopic dermatitis (mild/severe): ~35%
    • Asthmatic children: 6 - 8%
    • Prevalence depends on: Genetic factors, age, dietary habits, geography and diagnostic procedures
    Prevalence of food allergy Adapted from Sampson HA. Adverse Reactions to Foods. Allergy Principles and Practice. 2003
  • Food allergy in children: International USA & UK Milk Egg Peanut Tree Nuts Seafood FRANCE Egg Peanuts Milk Mustard ITALY Milk Egg Seafood ISRAEL Milk Egg Sesame SINGAPORE Birds Nest Seafood Egg Milk AUSTRALIA Milk Egg Peanuts Sesame
  • “ Second tier” foods
    • 10% reactions to foods
    • 160 foods
    • Fruits
    • Vegetables
    • Seeds (sesame, sunflower, poppy)
    • Spices
  • Pathophysiology: allergens
    • Proteins (not fat/carbohydrate) - 10-70 kD glycoproteins - Heat resistant, acid stable
    • Major allergenic foods (>85% of allergy) - Children: milk, egg, soy, wheat, other depending on geographical
    • area
    • - Adult: peanut, nuts, shellfish, fish
    • Single food (or related) > many food allergies
    • Characterization of epitopes underway - Linear vs conformational epitopes - B-cell vs T-cell epitopes
  • Food allergens
    • Class 1 food allergens:
      • Primary sensitizers
      • Sensitization may occur through the gastrointestinal tract
      • Water-soluble glycoproteins
      • Molecular weights ranging from 10 to 70 kD
      • Stable to heat, acid and proteases
    • Class 2 food allergens (cross-reactive):
      • Generally plant-derived proteins
      • Highly heat-labile
      • Difficult to isolate
      • No good, standardized, extracts are available for diagnostic purposes
    Adapted from Sampson HA. Adverse Reactions to Foods. Allergy Principles and Practice. 2003
  • Ma j or class 1 food allergens
    • Cow's milk:
    • Caseins (  ,  ,  ),  -lactoalbumin,  -lactoglobulin, serum albumin
    • Chicken egg:
    • Ovomucoid, ovalbumin, ovotransferrin
    • Peanut:
    • Vicillin, conglutin, glycinin
    • Lentil
    • Vicilin
    • Soybean:
    • Glycinin, profilin, trypsin inhibitor
    • Shrimp:
    • Tropomyosin
    • Fish:
    • Parvalbumins
    • Fruits and other vegetables (apple, apricot, peach, plum, corn)
    • Lipid transfer proteins (LTPs)
  • Class 2 food allergens (Cross-reactive and associated with oral allergy syndrome, latex-fruit syndrome)
    • Pathogen-related protein 2 group (glucanase):
    • Latex, avocado, banana, chestnut, fig
    • Pathogen-related protein 3 group (chitinase):
    • Latex (Hev b6), avocado
    • Pathogen-related protein 5 (thaumatin-like):
    • Cherry, apple, kiwi
    • Birch Bet v1 homologues (pathogen-related proteins 10):
    • Apple, cherry, apricot, peach, pear, carrot, celery, parsley, hazelnut
    • Birch Bet v2 homologues (celery-mugwort-spice syndrome) profilin:
    • Latex, celery, potato, pear, peanut, soybean
  • Prevalence of clinical cross reactivity among food “families”
    • Food Allergy Prevalence of Allergy to > 1 Food in Family
    • Fish 30-100%
    • Tree Nut 15-40%
    • Grain 25%
    • Legume 5%
    • Any 11%
  • Some cross-reactions between inhalant allergens and food allergens Van Ree R. Curr Opin Allergy Clin Immunol, 2004;4:235-40 Importance of considering 3-dimensional protein structure in prediction cross-reactivity Crustaceans Chironomids Banana, chestnut, kiwi, avocado Latex Tomato, peanut, pea, wheat, rye Grass pollen Melon, banana Ragweed pollen Nuts, apple, pear, peach, plum, cherry, carrot, peanut, soy Birch pollen Food allergy Inhalant allergy
  • Pathogenesis of food hypersensitivity: Gut barrier
    • The immune system associated with this barrier is capable of discriminating among harmless foreign proteins or commensal organisms and dangerous pathogens
    • Food allergy is an abnormal response of the mucosal immune system to antigens delivered through the oral route
    • The immature state of the mucosal barrier and immune system might play a role in the increased prevalence of gastrointestinal infections and food allergy in the first few years of life
    Adapted from J Allergy Clin Immunol 2004;113:808-809
  • Pathogenesis of food hypersensitivity: Gut barrier
    • About 2 % of ingested food antigens are absorbed and transported throughout the body in an immunologically intact form, even through the immature gut
    • The underlying immunologic mechanisms involved in oral tolerance induction have not been fully elucidated
    Adapted from J Allergy Clin Immunol 2004;113:808-809
  • Pathophysiology: immune mechanisms IgE-Mediated IgE-receptor Histamine
    • Protein digestion
    • Antigen processing
    • Some Ag enters blood
    Mast cell APC B cell T cell
    • TNF- 
    • IL-5
    Non-IgE- Mediated
  • Food Allergy: clinical manifestations
    • IgE IgE/Non-IgE Non-IgE
    Urticaria/angioedema Rhinitis /Asthma Anaphylaxis Oral allergic syndrome Gastrointestinal symptoms (GIT) Atopic dermatitis Eosinophilic gastro-intestinal disorders Protein-induced proctocolitis/enterocolitis Celiac disease Contact dermatitis Herpetiform dermatitis Heiner´s syndrome Adapted from J Allergy Clin Immunol. 1999;103:717-728
    • Acute Urticaria and Angioedema:
    • The most common symptoms of food allergic reactions
    • The exact prevalence of these reactions is unknown
    • Acute urticaria due to contact with food is also common
    • Chronic Urticar i a:
    • Food allergy is an infrequent cause of chronic urticaria and angioedema
    Cutaneous food hypersensitivities
  • IgE Mediated: respiratory manifestations
    • Asthma
    • An uncommon manifestation of food allergy
    • Usually seen with other food-induced symptoms
    • Vapors or steam emitted from cooking food may induced asthmatic reactions
    • Food-induced asthmatic symptoms should be suspected in patients with refractory asthma and history of atopic dermatitis, gastroesophageal reflux, food allergy or feeding problems as an infant, or history of positive skin tests or reactions to food
    • Rhinoconjunctivitis
    • Usually seen during positive controlled challenge tests, but occasionally reported by patients
  • IgE Mediated: systemic reaction anaphylaxis/anaphylaxis syndrome
    • Food-induced anaphylaxis - Rapid-onset - Multi-organ system involvement - Potentially fatal - Any food, highest risk: peanut, nut, seafood, milk, egg
    • Food-dependent - exercise-induced - Associated with a particular food - Associated with eating any food
  • Fatal food anaphylaxis
    • Frequency: ~ 100 deaths/yr
    • Risk: - Underlying asthma - Delayed epinephrine - Symptom denial - Previous severe reaction
    • History: known allergic food
    • Biphasic reaction
    • Lack of cutaneous symptoms
  • Gastrin Exercise Wheat Food-dependent, exercise-induced anaphylaxis Mediator release - Histamine - Others (LTD4,PAF, etc) Temperature ANAPHYLAXIS Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and Clinical Immunology
  • IgE-mediated: GIT manifestation oral allergy syndrome (OAS)
    • Elicited by a variety of plant proteins that cross-react with airborne allergens
    • Pollen allergic patients may develop symptoms following the ingestion of vegetable foods:
      • - Ragweed allergic patients: Fresh melons and bananas
      • - Birch pollen allergic patients: Raw potatoes,
      • carrots, celery, apples, pears, hazelnuts and kiwi
    • Immunotherapy for treating the pollen-induced rhinitis may reduce/eliminate oral allergy symptoms
    Adapted from J Allergy Clin Immunol. 2004; 113:808-809
    • Generally begins in early infancy
    • Characterized by typical distribution, extreme pruritus, and chronically relapsing course
    • Allergen-specific IgE antibodies bound to Langerhans cells play a unique role as “non-traditional” receptors
    • Double blind, placebo-controlled food challenges generally provoke a markedly pruritic, erythematous, morbilliform rash
    • Food allergy plays a pathogenic role in about 35 % of moderate-to-severe atopic dermatitis in children
    Cutaneous food hypersensitivities: atopic eczema
  • Food allergy prevalence in specific disorders Rare Chronic rhinitis 5-6% in asthmatic or food allergic children Asthma 20% in acute (rare in chronic) Urticaria 35% in children (rare in adults) Atopic dermatitis 25-75% in pollen allergic Oral allergy syndrome 35 – 55 % Anaphylaxis Food Allergy Prevalence Disorder
    • Characterized by infiltration of the esophagus, stomach and/or intestinal walls with eosinophils, basal zone hyperplasia, papillary elongation, absence of vasculitis and peripheral eosinophilia in about 50 % of patients
    • AEE can occur in children and adults. Increasing yearly incidence (23/100.000 population in Switzerland)
    • In children symptoms similar to gastroesophageal reflux and in adults dysphagia and impaction is common
    • Almost 50% of patients have other atopic diseases
    • Diagnosis is based on endoscopic findings and biopsy (>15-20 eosinophils per High Power Field)
    Mixed IgE/Non-IgE mediated: GIT allergic eosinophilic disorders Adapted from J Allergy Clin Immunol. 2006; 118:1054-9
    • Dysphagia
    • Abdominal pain
    • Poor response to anti - reflux drugs
    • Biopsy:Eosinophils ++++ >20 eosinophils / HPF
    • Eotaxin – 3 tissue expression correlates with eosinophilia – crucial in pathogenesis of this disorder
    Mixed IgE/non-IgE mediated: GIT allergic eosinophilic esophagitis (AEE) Bullock et J Pediatr Gastroenterol Nutr. 2007
  • Allergic eosinophilic esophagitis endoscopic findings Rings White plaques (eosinophils)
    • Weight loss, FTT+/_oedema
    • Vomiting, diarrhoea (post-prandial)
    • Blood loss
    • Iron deficiency
    • Protein/iron- losing enteropathy
    • ↑ TH2 in blood and mucosa
    • ↑ Mast cells, Eosinophils in mucosa
    • Eotaxin - 3
    • Persistent food hypersensitivity at 5yr FU.
    Mixed IgE/non-IgE mediated: GIT allergic eosinophilic gastroenteritis (AEG) Chehade M et al JPGN 2006;42;516-521
    • Food antigens have been implicated as one of the main etiologies
    • Skin prick test and atopy patch tests can be useful for food allergy diagnosis
    • Elimination diets or even amino-acid formula can be instituted on the basis of allergy testing, clinical history, biopsy and treatment response
    • Pharmacologic treatment: oral steroids and/or swallowed aerosolized fluticasone
    • ? Anti-IL-5 therapy
    AEE and AEG Adapted from J Allergy Clin Immunol. 2006; 118:1054-9
  • Non-IgE mediated: GIT food protein induced syndromes ( typically milk and soy induced)
    • Enterocolitis # Enteropathy Proctocolitis
    • Age Onset: Infant Infant/Toddler Newborn
    • Duration: 12-24 mo ? 12-24 mo < 12mo
    • Characteristics: Failure to thrive Malabsorption Bloody stools Shock Villous atrophy No systemic sx Lethargy Diarrhea Eosinophil Diarrhea
    # Solid foods implicated: fish, corn, chicken, turkey, vegetables Nowak-Wegrzyn et al Pediatrics 2003 Zapatero Remon L et al. Allergol Immunopathol 2005
    • Occurs in infants prior to 8-12 months of age, but may be delayed in breast-fed babies (milk or soy protein-based formulas are implicated)
    • Symptoms may include irritability, protracted vomiting 1- 3 hours after feeding, bloody diarrhoea (leading to dehydration), anaemia, abdominal distension, failure to thrive
    • In adults and older children, fish, shellfish and cereals hypersensitivity may provoke a similar syndrome with delayed onset of severe nausea, abdominal cramps and protracted vomiting
    • Resolved: 50% at 18 months, 90% at 36 months
    Non IgE mediated: GIT food protein-induced enterocolitis syndrome Adapted from J Allergy Clin Immunol. 2004; 113:808-809
    • Occurs from 0 - 24 months
    • Diarrhea (mild to moderate steatorrhea in about 80% of cases)
    • Food implicated: milk, cereals, egg, fish
    • Poor weight gain
    • Diagnosis:
    • -Biopsy shows patchy villous atrophy with prominent mononuclear round cell infiltrate, few eosinophil s,
    • -Response to exclusion diet,
    • -Challenge test
    • Resolved at 2 - 3 years old
    Non-IgE Mediated: GIT food protein-induced enteropathy (excluding celiac disease) Adapted from J Allergy Clin Immunol. 2004; 113:808-809
    • Usually presents in the first few months of life and is thought to be due to food proteins passed to the infant in maternal breast milk, or to milk or soy-based formulas
    • Rectal bleeding is common
    • Diagnosis: endoscopy and colonic biopsy (eosinophils in epithelium and lamina propia)
    • Good response to extensively hydrolized formulas. Diet without dairy product in mother if lactating
    • Good prognosis with resolution at 12 months of life
    Non-IgE Mediated: GIT food protein-induced protocolitis Adapted from J Allergy Clin Immunol. 2004; 113:808-809
  • Non-Ige Mediated: GIT celiac disease
    • Extensive enteropathy leading to malabsorption
    • Associated with an immune reaction to gliadin peptides (wheat, rye and barley)
    • Highly associated with HLA-DQ2  1 *0501.  1 *0201)
    • Serology: anti-transglutaminase IgA, Anti-gliadin IgA (asymptomatic and +ve serology is common)
    • Treatment: Elimination of gluten-containing foods
    Adapted from J Allergy Clin Immunol. 2004; 113:808-809
  • Non-IgE-mediated syndromes affecting the skin and lung
    • Dermatitis Herpetiformis - Vesicular, pruritic eruption - Gluten-sensitive - Associated with Celiac Disease
    • Heiner’s Syndrome - Infantile pulmonary hemosideroisis - Anemia, failure to thrive - Cow’s milk-associated - Precipitating antibodies to cow’s milk
  • Gastrointestinal food hypersensitivity? Infantile colic
    • Syndrome of paroxysmal fussiness characterized by inconsolable, agonized crying
    • Generally develops in the first 2 to 4 weeks of life and persists through the third to fourth months
    • Diagnosis can be established by the implementation of several brief trials of hypoallergenic formula
    Adapted from J Allergy Clin Immunol. 2004; 113:808-809
  • Disorders not proven to be related to food allergy
    • Migraines
    • Behavioral/Developmental disorders
    • Arthritis
    • Seizures
    • Inflammatory bowel disease
  • Diagnosis: history/examination
    • History: symptoms, timing, reproducibility
      • Acute reactions vs chronic disease
    • Diet details / symptom diary
      • Specific causal food/s
      • “ Hidden” ingredient/s
    • Physical examination: Evaluate disease severity
    • Identify general approach
      • Allergy vs intolerance
      • IgE-mediated vs non-IgE mediated
    • Identification and relationship with the food: Medical history
    • To identify specific IgE: Skin tests/serum specific IgE
    • To demonstrate that IgE sensitization is responsible for the clinical reaction: Controlled challenge tests
    • Diagnosis is based on the medical history, supported by identification of specific IgE antibodies to the incriminated food allergen and confirmed by challenge
    Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and Clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62.   Diagnosing food hypersensitivity disorders: IgE-mediated
    • Symptoms described by patient
    • Length of time between ingestion and development of symptoms
    • Severity of symptoms
    • Frequency of symptoms
    • Time from last episode
    Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62. Diagnosing IgE-mediated food hypersensitivity disorders Medical history: Symptoms
    • An immediate reaction (1- 2 hours) is suggestive of an IgE mediated reaction to foods
      • It may be preceded by previous tolerance of minimal symptoms
      • It may occur apparently after the first contact
    Diagnosing IgE-mediated food hypersensitivity disorders Medical history: Timing of reaction Adapted from Adverse Reactions to Foods Committee, Spanish Society of Allergy and Clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62.
    • Identification of food
    • How food was prepared
    • Quantity ingested
    • Previous tolerance
    • Cross-reactions with other food
    • Hidden foods, additives, contaminants
    Diagnosing IgE-mediated food hypersensitivity disorders Medical history: food Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62.
  • Diagnosing IgE-mediated food hypersensitivity disorders
    • Age at onset of symptoms
    • Other factors (eg, brought on by exercise)
    • Personal and family history of atopic diseases
    • Risk factors
    • Physical examination: Atopic dermatitis, dermographism, nutritional status
    Medical history: Patient Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62.
    • The diagnosis of food allergy cannot be performed on the basis of a non-compatible medical history
    • No diagnostic analysis (skin tests, specific IgE in serum, etc) is of value if it is interpreted without reference to medical history
    Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and Clinical Immunology Alergol Inmunol Clin 1999; 14: 50-62. Diagnosing IgE-mediated food hypersensitivity disorders
  • Clinical symptoms compatible with allergic reaction to food Immediate reactions (from minutes to 1- 2 hours) after ingestion/contact/inhalation with food Late gastrointestinal or atopic dermatitis reactions (>2 hours) Any age After last reaction, patient could not tolerate the food Early correct positive diagnosis allows a suitable diet to be followed and avoids the risks of inappropriate dietary restrictions Negative diagnosis avoids unnecessary dietary restrictions Allergy Assessment
    • Prick: Reproducible, sensitive, not irritant
    • Prick-prick: Use raw or cooked food. Highly recommended for fruits and vegetables (commercially prepared extracts are generally inadequate because of the lability of the allergens, so the fresh food must be used for skin testing)
    Diagnosing IgE-mediated food hypersensitivity disorders Skin tests
    • Skin Prick Tests are used to screen patients for sensitivity to specific foods
    • Allergens eliciting a wheal of at least 3 mm greater than the negative control are considered positive
    • Overall positive predictive accuracy is < 50 %
    • Negative predictive accuracy > 95 % (negative skin test results essentially confirm the absence of IgE-mediated reactions)
    Diagnosing IgE-mediated food hypersensitivity disorders + Diameter  3 mm
    • In infants younger than 2 years, skin prick tests to milk, egg, or peanut with wheal diameters of at least 8 mm are more than 95% predictive of reactivity
    • In general, negative skin prick test results are extremely useful for excluding IgE-mediated food allergies, but positive skin test results are only suggestive of presence of clinical food allergies
    • There is no correlation between the size of wheal and the clinical sensitivity in individual patients
    Diagnosing IgE-mediated food hypersensitivity disorders
  • Diagnosis of IgE-mediated food allergy: Skin prick testing Sporik et al. Clin Exp Allergy 2000; 30: 1540-6 Skin Prick Testing 100% Pos i tive Predictive values (PPV) Food 100% PPV  2 yrs (wheal diameter) 100% PPV  2 yrs (wheal diameter) Cow's milk 8mm 6mm Egg  7mm 5mm Peanut  8mm 4mm ≥
    • Intradermal: Not indicated
    • Atopy Patch test (APT): Atopic dermatitis, delayed reactions
    • Fresh food or dry food recommended
    • Non-standarized
    • Difficult to interpret
    Diagnosing IgE-mediated food hypersensitivity disorders Skin tests
    • Sensitivity similar to skin prick tests
    • Good correlation with other procedures
    • Efficiency: Depends on the allergen
    • Indicated if SPT are contraindicated (eg, skin disease, medications)
    • Useful if discrepancy exists between history and SPT
    • The use of quantitative measurements has shown to be predictive, for some allergens, of symptomatic IgE-mediated food allergy
    • Possibility to perform component-resolved diagnosis very useful in cross-reactivity reactions: profilins (Bet v2, Phl p12), polcalcins (Bet v4, Phl p7), LPT (Pru p3, Cor a8), Gly m4, Cross-reactive Carbohydrate Determinants or CCDs
    Specific IgE to food (CAP / Radioallergosorbent tests)
  • Diagnostic food-specific IgE values (CAP-system fluorescent enzyme immunoassay) of greater than 95% positive predictive value
    • Food Serum IgE Value (kU/L)
    • Egg ≥7.0
    • ≤ 2 yr old ≥2.0*
    • Milk ≥15.0
    • ≤ 2 yrs old ≥5.0**
    • Peanut ≥14.0
    • Fish ≥20.0
    • Tree nuts ≥15.0
    • From Sampson HA: JACI 107:891-896,2001 .
    * Boyano-Martinez T, Garcia-Ara C, Diaz-Pena JM, et al: Clin Exp Allergy 31:1464-1469,2001. ** Garcia-Ara C, Boyano-Martinez T, Diaz-Pena JM, et al: JACI 107:185-190,2001.
    • Advantages
    • Multiple determinations with one blood sample
    • Quantitative and comparable measurements
    • Use of recombinant allergens
    • Component-resolved diagnosis
    • Disadvantages
    • Cost
    • Results delayed
    Diagnosing IgE-mediated food hypersensitivity disorders Serum specific IgE (CAP / RAST)
  • Interpretation of laboratory tests
    • Positive prick test or RAST / CAP
    • - Indicates presence of IgE antibody NOT clinical reactivity ( ~50% false positive)
    • Negative prick test or RAST - Essentially excludes IgE antibody (>95%)
    • Intradermal skin test with food - Risk of systemic reaction & not predictive
  • Cross-reactivity among foods
    • Patients often have positive SPTs or RAST results to other members of a plant family or animal species - immunological reactivity – does not always correlate with clinical reactivity
    • Cross reactions caused primarily by “Type 1” sensitization Legumes, tree nuts, fish, shellfish, cereal grains, mammalian and avian food products
    • Cross reactions caused by “Type 2” sensitization
    • - Pollen-food allergy syndrome (oral allergy syndrome),
    • - Latex- food syndrome
    • Proper clinical evaluation (ideally by double-blind placebo-controlled challenge testing) is necessary in patients who demonstrate immunological cross-reactivity to foods and when tolerance to food is unknown (to avoid unnecessary restriction of certain foods)
  • Cross reactions with foods: clinical implications
    • If the patient is diagnosed with allergy to a food, assessment of clinical sensitization to foods with known cross reactivity is recommended
    • If the patient is diagnosed with allergy to a food with known cross reactivity with another food which he / she is not eating (unknown tolerance) that food must be challenged to assess tolerance
  • Cross reactivity in food allergy: clinical relevance Scott H. Sicherer. AAAAI San Francisco 2004:Seminar 3508. OAS = Oral Allergy Syndrome CMA = Cow’s Milk Allergy
  • Diagnosing IgE-mediated food hypersensitivity disorders
    • Histamine release with foods:
    • Similar sensitivity and specificity to serum specific IgE
    • Sulphidoleukotrienes released from basophils with food: Not well studied
    • For monitoring food challenges:
    • - Plasma and urinary histamine: High sensitivity, low
    • specificity
    • - Serum tryptase: High specificity, low sensitivity
    Other Techniques
  • Unproven / experimental tests (useless)
    • Provocation / neutralization
    • Cytotoxic tests
    • Applied kinesiology
    • Hair analysis
    • IgG 4
  • Diagnosis: Elimination diets and food challenges
    • Elimination diets (1 - 6 weeks): - Eliminate suspected food/s, or - Prescribe limited “eat only” diet, or - Elemental diet
    • Oral challenge testing: - Physician supervised - Emergency room medications must be available
  • Basic elimination diet: ALLOWED foods
    • Rice
    • Fruit: Pear, Apple, Grape
    • Meat: Lamb, Chicken
    • Vegetables: Asparagus, Beetroot, Carrots, Lettuce, Sweet potatoes, Butternut Squash
    • Other: Black Tea, Rooibos
    • Olive oil, Sunflower oil, Sugar, Salts
    • NB: No Preservatives, no tinned or packet foods
    • Patients of any age with history of adverse reaction to a food :
    • For establishment or exclusion of the diagnosis of food intolerance / allergy
    • For scientific reasons in clinical studies
    • For determination of the threshold value or degree of sensitivity
    • For assessment of tolerance - once diagnosed, when a patient is suspected to have outgrown clinical allergy -especially in children, because food allergies are normally outgrown during childhood (eg, milk or hen’s egg allergies)
    Controlled food challenges: Inclusion criteria (IgE-mediated allergy) EAACI Position Paper, Allergy 2004; 59: 690-697
    • Repetitive reactions with minimal quantities of food with positive SPT / CAP-RAST
    • Recent (children) severe systemic reaction or (adults) anaphylaxis
    • In selected cases where positive test results makes challenge unnecessary (e.g. Children with convincing history to egg and +ve SPT and specific IgE (CAP)  17.5 Ku/L to egg )
    When a controlled food challenge is not necessary for diagnosing food allergy
  • Controlled food challenges
    • Patient without symptoms, and fasting
    • The quantity of food to start the challenge may depend upon the quantity of food that induced the last reaction
    • Is highly recommended to start with minimal doses, with a slight increase at intervals superior to the latency period that the patient has experienced in previous reactions
    Methods
  • Controlled food challenges
    • The quantity of the last challenge dose will be related to the age of the patient (normal amount)
    • Challenge with different foods on different days
    • In asthma ensure long wash-out periods, FEV1 ≥ 80%, and follow-up with FEV 1 or peak expiratory flow (PEF) hourly for 6 hours
    • Atopic eczema and chronic urticaria: If partial improvement after exclusion diet and on minimal treatment
    Methods
  • Types of challenge testing
    • Double -blind
    • Single-Blind
    • Open
    • Exercise + oral challenge
    • Inhalation challenge
    • DB is the procedure generally recommended, especially if a positive challenge outcome is expected
    • DB is the method of choice for scientific protocols
    • DB is the method of choice when studying late reactions or chronic symptoms, such as atopic eczema, isolated digestive late reactions, or chronic urticaria
    • DB is the only way to conveniently study subjective food-induced complaints, such as acute subjective adverse reactions, chronic fatigue syndrome, multiple chemical sensitivities, migraine or joint complaints
    Controlled food challenges: Double-blind, placebo-controlled (DBPCFC) EAACI Position Paper. Allergy 2004; 59: 690-697
  • Controlled food challenges: Eligible patients for DBPCFC include
    • All patients with suspicion of an immediate, systemic allergic reaction to a food, for establishment or exclusion of the diagnosis
    • Infants and children  three years: An open challenge controlled and evaluated by a physician is most often sufficient
    • Patients with pollen related oral allergy syndrome as their only symptom should only undergo DBPCFC in selected cases; eg, in cases with discrepancy between the case history and the outcome of in vivo and/or in vitro tests
    EAACI Position Paper. Allergy 2004; 59: 690-697
  • Controlled food challenges: Double-blind, placebo-controlled (DBPCFC)
    • An open challenge may precede DBPCFC in older children and adults because a negative result renders DBPCFC unnecessary
    • Open challenges should not be applied in cases with a high probability of a positive outcome, or in cases with subjective and/or controversial symptoms only
    EAACI Position Paper. Allergy 2004; 59: 690-697
  • Placebo controlled food challenges
    • Intercalate food and placebo
    • Active and placebo should have identical characteristics and ensure allergenicity
    • Masking of food: Appearance, colour, flavor, texture
    • Placebos: Dextrose, liquids
    • Vehicles: Capsules (lyophilized)
    • Liquids (placebo)
    • There are many recipes published for masking foods.
    • Capsules: Limit quantity (cereals, dry fruits)
    • Avoid contact with oral mucosa (not used in oral allergy syndrome)
  • Double-blind, placebo-controlled food challenge testing: Limitations
    • Tedious
    • Time-consuming and expensive
    • Potential risk requires specialist unit (research)
    • IgE-mediated or non-IgE-mediated?
  • Controlled food challenges: Single-blind challenge
    • Single-blind challenge carries the same difficulties for blinding foods as for double-blind, and introduces subjective bias of the observer
    • It needs additional work (cross-over by an external technician)
    • The recommendation of the European Academy of Allergology and Clinical Immunology is to always perform double-blind food challenge
    EAACI Position Paper. Allergy 2004; 59: 690-697
    • A negative double-blind challenge should always be followed by an open challenge
    • A positive open challenge could be sufficient when dealing with IgE-mediated acute reactions manifesting with objective signs
    • For practical reasons, an open challenge can be the first approach when the probability of a negative outcome is estimated to be very high
    Controlled food challenges: Open challenge EAACI Position Paper. Allergy 2004: 59: 690-697
    • In infants and children  3 years, an open, physician-controlled challenge is often sufficient for suspected immediate type reactions (unless a psychological reaction of the mother is expected)
    • For patients with pollen-related oral allergy syndrome as their only symptom, an open challenge could be sufficient as a regular procedure. However, double-blind challenge is recommended for scientific protocols and other selected cases for example, when discrepancies exist between the clinical history and the outcome of diagnostic tests
    Controlled food challenges: Open challenge EAACI Position paper Allergy 2004: 59: 690-697
  • Diagnostic approach: IgE-mediated allergy
    • Test for specific-IgE antibody - Negative: Reintroduce food* - Positive: Start elimination diet
    • Elimination diet - No resolution: Reintroduce food* - Resolution - Open/single-blind challenges to “screen” - DBPCFC for equivocal open challenges
    • * Unless convincing history warrants supervised challenge
  • Diagnostic approach: Non-IgE-mediated disease
    • Includes disease with unknown mechanisms - Food additive allergy
    • Elimination Diets (may need elemental diet)
    • Oral Challenges - Timing / dose / approach individualized for disorder - Enterocolitis syndrome can elicit shock - Enteropathy / eosinophilic gastroenteritis-prolonged feedings to develop symptoms
    • May require ancillary testing (endoscopy / biopsy)
  • Food allergy: Treatment
    • Correct diagnosis
    • Treatment of reactions
    • Avoidance
    • Role of dietician
    • Tolerance assessment
    • Prevention
    • Immunotherapeutic strategies
    Adapted from Adverse Reactions to Foods Committee. Spanish Society of Allergy and Clinical Immunology
  • Treatment emergency medicines
    • Epinephrine: drug of choice for reactions - Self-administered epinephrine readily available - Train patients: Indications / technique
    • Antihistamines: Secondary therapy
    • Emergency plan in writing - Schools, spouses, caregivers, mature siblings / friends
    • Emergency identification bracelet
  • Treatment: Avoidance
    • Mainstay of treatment
    • Must be considered as a therapeutic approach
    • Risk-benefit must be assessed
      • - Correct diagnosis is essential
      • - Very restrictive diets can lead to malnutrition
    • Dietician’s role is crucial
  • Vitamins and minerals which will be affected by restricted diet Vitamin E, niacin, magnesium, manganese, & chromium Peanut Thiamin, riboflavin, niacin, iron, & folate if fortified Wheat Thiamin, riboflavin, pyridoxine, folate, calcium, phosphorus, magnesium, iron, & zinc Soy Vitamin B12, riboflavin, pantothenic acid, biotin, & selenium Egg Vitamin A, vitamin D, riboflavin, pantothenic acid, vitamin B 12 , calcium, & phosphorus Milk Vitamin and Minerals Allergen
  • Treatment: Dietary elimination
    • Hidden ingredients
    • Labelling issues
    • Cross contamination (shared equipment)
    • “ Code words” (“Natural flavor” may be cow’s milk)
    • Seeking assistance Registered dietician: ( www.eatright.org )
    • Food Allergy Network ( www.foodallergy.org ) (800-929-4040)
  • Hidden foods
    • Some foods (allergens) are masked and may be taken
    • un-noticed during diagnostic procedure:
      • Spices: Mustard, pepper, sesame
      • Legumes and tree nuts: Peanut, soy
      • Milk protein (protein supplements): Caseine, caseinates
      • Vaccines
      • Kitchen tools, volatile allergens
      • Transgenic foods with new proteins
    • Parasitized food:
      • Mites in flour ( pasta, pizzas)
      • Anisakis simplex in fish
    READ LABELS IN PREPARED FOOD!!!
  • Example: Milk elimination
    • Artificial butter flavor, butter fat, buttermilk, casein, caseinates (sodium, calcium, etc), cheese, cream, cottage cheese, curds, custard, Half&Half ®, hydrolysates (sasein, milk, whey), lactalbumin, lactose, milk (derivatives, protein, solids, malted, condensed, evaporated, dry, whole, low-fat, non-fat, skim), nougat, pudding, rennet casein, sour cream, sour cream solids, sour milk solids, whey (delactosed, demineralized, protein concentrate), yogurt. MAY contain milk: brown sugar flavoring, natural flavoring, chocolate, caramel flavoring, high protein flour, margarine, Simplesse®
  • Substitute infant formulas
    • Soy (confirm soy IgE negative) <15% soy allergy among IgE-cow’s milk allergy ~50% soy allergy among non-IgE cow’s milk allergy
    • Cow’s milk protein hydrolysates: 90% tolerance in IgE-cow’s milk allergy
    • Partial hydrolysates: Not hypoallergenic!
    • Amino acid-based formulas: Lack allergenicity
  • Natural history
    • Dependent on food & immunopathogenesis
    • IgE-mediated allergy: - CM 85% remit by 8 yrs Saarinen et al JACI 2005 - Egg 66% remit after 5 yrs Bovano-Martinez et al JACI 2002 - Peanut 20% may remit (8% may recur) Fleischer et al JACI 2004 - Treenut, seafood typically persist
    • Declining/low levels of specific-IgE predictive
    • Non-IgE-associated GI allergy - Infant forms resolve 1- 3 years - Toddler/adult forms more persistent
  • Treatment: Follow-up
    • Re-evaluate for tolerance periodically
    • Interval and decision to re-challenge: - Type of food allergy - Severity of previous symptoms - Allergen
    • Ancillary testing - Skin prick test/RAST/CAP may remain positive - Reduced concentration specific-IgE encouraging
  • Food specific IgE cut off levels which predict 50% pass rate for challenge tests
    • Food IgE level (KUA/l)
    • Milk 2
    • Egg 2
    • Peanut 2
    • Wheat ?
    • Soy ?
    Perry et al. JACI 2004
  • Prevention of food allergy / allergic disease
    • Identify patients at risk (difficult)
      • There is no reliable or genetic immunological marker
      • Atopic background in parents, siblings
    • Dietary restriction (milk, egg, fish, nut)
      • In pregnancy: No benefit
      • Adverse events on maternal-fetus nutrition
      • Hydrolyzed formula (HF): Variable effect ( Cochrane Database Syst Rev. 2006 Oct 18); GINI Study, JACI Mar 2007; extensively HF & partially HF reduce incidence of AD, but not that of asthma
      • Delayed introduction of solid food: Variable effect ( Ann Allergy Asthma Immunol. 2006;97:10-20)
    • Prolonged breast feeding?
    • Probiotics??
  • Future immunomodulatory therapies
    • Humanized anti-IgE monoclonal antibody therapy
    • “ Engineered (mutated) allergen protein immunotherapy
    • Antigen-immunostimulatory sequence (CpG)-modulated immunotherapy
    • Peptide immunotherapy
    • Plasmid-DNA immunotherapy
    • Cytokine-modulated immunotherapy
    • Induction of tolerance or oral immunotherapy (milk, egg, hazelnut…….)
  • Summary
    • IgE & non-IgE mediated food allergy conditions exist
    • History and examination paramount
    • Diagnosis is by elimination and challenge testing
    • Avoidance / education / preparation for emergencies are current therapies
    • Periodic re-challenge to monitor tolerance as indicated by history, allergen, and level of food specific-IgE
  • World Allergy Organization (WAO) For more information on the World Allergy Organization (WAO), please visit www.worldallergy.org or contact: WAO Secretariat 555 East Wells Street, Suite 1100 Milwaukee, WI 53202 United States Tel: +1 414 276 1791 Fax: +1 414 276 3349 Email: [email_address]
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