Food allergy slide

Food Allergy IRachanont [email protected]

18 feb 2009

ABC of allergiesFood allergyCarsten Bindslev-Jensen

The public perceives food allergy differently fromdoctors—especially in relation to its symptoms and prevalence.In controlled scientific studies a low prevalence of food allergyhas been found in British and Dutch adults, whereas thepercentage of people perceiving their illness as being fooddependent is much higher. The prevalence in adults, confirmedby double blind, placebo controlled food challenge, has beenestimated to be 1.4%. This is in contrast to findings in children,in whom the overall prevalence of IgE mediated food allergiesis 5-7%.

DefinitionsAdverse reactions to foods may be classified as due to eithertrue food allergy or non-allergic food intolerance. In contrast,food aversion refers to symptoms that are often non-specificand unconfirmed by double blind, placebo controlled foodchallenge.

A true food allergy is a disorder in which ingestion of asmall amount of food elicits an abnormal immunologicallymediated clinical response. Food may cause allergic reactions byseveral mechanisms. The classic type I, IgE mediated reaction isthe most thoroughly studied and potentially important in viewof the risk of life threatening reactions in some people.Evidence is increasing, however, for an important role fordelayed reactions (classic type IV mediated reactions). Forexample, eczema in children may be exacerbated by milkingestion, and a small proportion of adults with severe contactdermatitis due to nickel may react to nickel in their diet.

Non-allergic food intolerance may be due topharmacological, metabolic, and toxic causes. Pharmacologicalcauses may provoke anaphylactoid reactions, flushing,hypotension, and urticaria. This can happen with foods with ahigh histamine content (for example, scombroid poisoning dueto ingestion of brown oily fish (mackerel, tuna, etc) that has goneoff). Tyramine in cheese or red wine may provoke or exacerbatemigraine. Monosodium glutamate may provoke flushing,headache, and abdominal symptoms (the Chinese restaurantsyndrome). Lactase deficiency in young children is an exampleof non-allergic food intolerance due to a metabolic cause, and itmanifests as abdominal symptoms and chronic diarrhoea afteringestion of milk. Toxic reactions to foods may be due tocontamination of food by chemicals or bacterial toxins.

Much overlooked is the harmless, non-immunologicallymediated, immediate perioral flare reaction (non-immunologicalcontact urticaria) to, for example, benzoic acid from citrus fruitsin children (especially those with atopic dermatitis). Parents anddoctors may misinterpret this response in a child as an allergyand unnecessarily stop the child from eating citrus fruits. Foodadditives and colourings may elicit an acute flare up reaction ofurticaria and, more rarely, gastrointestinal symptoms, with orwithout exacerbation of urticaria, asthma, or rhinitis. Additivesinclude benzoates, salicylates, sulphites, and tartrazine and othercolourings. The diagnosis of these reactions should be suspectedin patients who develop symptoms on exposure to foods thatcontain preservatives—for example, meat pies, sausages and otherpreserved meats, dried fruits that contain sulphite, and manycommercially tinned and bottled foods. Preservatives may also be

Prevalence (%) of adverse reactions to foods in adults*

Town

Perceivedprevalencein adults

Confirmedprevalence†

High Wycombe 20.4 1.4

*Data from Young et al (Lancet 1994;1127-30).†With double blind, placebo controlled food challenge.

Types of adverse reactions to foodsx Food allergy due to IgE mediated mechanism (Coombs’

classification, type I)x Food allergy not involving IgE, in which other immunological

mechanisms are implicated (for example, type IV)x Non-allergic food intolerance (for example, pharmocological,

metabolic, or toxic reactions to foods)x Food aversion (symptoms are often non-specific and unconfirmed

by blinded food challenge)

Common products containing preservatives

Clinical review

1299BMJ VOLUME 316 25 APRIL 1998 www.bmj.com

on 4 January 2009 bmj.comDownloaded from

Wednesday, February 18, 2009

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การแพ้อาหารคือ การผิดปกติของร่างกายเมื่อทานอาหารบางอย่าง เข้าไป โดยสาเหตุของความผิดปกติเกี่ยวข้องกับระบบภูมิคุ้มกันของร่างกาย


Adverse food reaction

เกี่ยวข้องกับระบบภูมิคุ้มกัน

ไม่เกี่ยวข้องกับระบบภูมิคุ้มกัน


Immunologic

IgE mediated reaction

การเกิด Anaphylactic shock จากการแพ้ถั่วลิสง

อาการคัน และบวมที่ริมฝีปาก เยื่อบุช่องปากหลังจากทานอาหารบางอย่าง


Immunologic

Non IgE mediated reaction

protein – induced enterocolitis syndrome

Celiac disese


Food intolerances

Toxic reactions

เกิดอาหารเป็นพิษจากเชื้อโรค หรือโลหะหนักที่ปนอยู่ในอาหาร

ได้รับพิษจากปลาปักเป้า

การดื่มกาแฟ หรือแอลกอฮอล์มากเกินไป


Food intolerances

Non – toxic reaction

แพ้นม (lactose intolerance)

Pancreatic insufficiency

Galactosemia


Food dependent exercise – induced anaphylaxis

Wheat

Mediator release

- Histamine

- Others (LTD4,PAF, etc)

Temperature


Prevalence of Food Allergy

ประชากรอเมริกากว่า 20 % คิดว่าตนเองแพ้อาหาร

จากการสํารวจพบว่าเด็กประมาณ 6 % และผู้ใหญ่ประมาณ 4 % แพ้อาหารจริง



IgE-Mediated

IgE-receptor

Histamine

!!Protein digestion

!!Antigen processing

!!Some Ag enters blood

Mast cell APC

B cell T cell !!TNF-!

!!IL-5

Immune Mechanism


Signs and Symptoms

SKIN

Hives/angioedema

Flushing

Papular rash

Pruritis

GASTROINTESTINAL

Itching or swelling of lips, tongue, mouth

Nausea

Vomiting or reflux

Abdominal cramping

Diarrhea


Signs and Symptoms

RESPIRATORY

Congestion, itching, sneezing, runny nose

Laryngeal edema, cough, hoarseness

Wheezing, shortness of breath, chest tightness

CARDIOVASCULAR

Feeling of faintness

Syncope

Hypotension/shock

Arrhythmias


DiagnosisHistory: symptoms, timing, reproducibility

Acute reactions vs chronic disease

Diet details: specific causal food(s)

“Hidden” ingredient(s) less likely

Physical examination: evaluate other allergic conditions

Identify general mechanism

Is it food related at all?

Allergy vs. intolerance

IgE versus non-IgE mediated


DiagnosisSuspect IgE-mediated

Prick skin tests (commercial or fresh food)

CAP RAST

Suspect non-IgE-mediated

Consider elimination diet, GI evaluation

Suspect non-allergic, consider:

Breath hydrogen test (lactose intolerance)

Sweat test (cystic fibrosis)

Endoscopy


Diagnostic Approach to Evaluating Food Allergy


Skin prick test (SPT)Skin prick test (SPT) เป็นวิธีที่ไว และถูกที่สุดในการวินิจฉัยการแพ้อาหาร สามารถทําได้โดยไม่ต้องมีสารมาตรฐานเปรียบเทียบ แต่ผู้เชี่ยวชาญบางคนก็แนะนําให้ใช้น้ําแอปเปิ้ลสดเป็นตัวควบคุมเพื่อ rule – out Non IgE mediated reaction

TestingStandardised food extracts are rarely available for use in skinprick testing to diagnose food allergy. However, a few foodextracts have been validated in clinical trials in children andadults by using a double blind, placebo controlled foodchallenge as the gold standard. Foods that have been validatedin this way include cod, peanuts, cows’ milk, hens’ eggs, shrimps,and soy beans. In many cases it is better and more convenient touse fresh fruits for skin prick testing. A drop of liquid food or apiece of solid food is placed on the forearm and prickedthrough (the “prick-prick” method).

The same reservations expressed for skin pricktesting—namely, poorly standardised food allergen extracts—arealso true for the various methods for determining serumconcentrations of allergen-specific IgE against food. Anothermajor problem with the newer and technically highly sensitivemethods is that they detect the many clinically insignificantserological cross reactions, in which IgE raised against anddirected towards epitopes on, for example, grass pollen, alsobinds to wheat proteins, but without any clinical significance ofthe finding.

The significance of reactions to patch testing is currentlybeing evaluated in several centres. However, before any new testis included for routine diagnosis, it should be validated inclinical trials with a double blind, placebo controlled foodchallenge as the gold standard.

Confirmation with oral food challengeDouble blind, placebo controlled food challenge may be neededto confirm the medical history of and positive diagnostic testsfor food allergy. Most published studies show that in an averageof 50% of patients whose medical history plus positive skinprick test result or positive IgE result suggest food allergy,allergy can be confirmed by a double blind, placebo controlledfood challenge. Using fresh foods masked in a vehicle is betterthan using freeze dried foods in capsules. In selected cases anopen challenge (that is, not double blind or placebo controlled)

Results of allergen-specific IgE should beinterpreted with caution, especiallyweakly positive results in patients withhigh serum concentrations of total IgE

Fresh fruit can be used for skin prick testing for fruit allergy

Cross reactivity between birch pollen and apple in patient withspringtime hay fever and oral allergy syndrome after ingestion ofapple

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reSy

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om s

core

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1 2

Strict elimination diet

Restricted diet Restricted dietOffending foods

3 4 5 6 7 8 9 10Week

Top: Effect on symptoms of introducing restricted diet (elimination ofsuspected offending food) then reintroducing normal diet then returning torestricted diet in a patient who was eventually confirmed as being allergic towheat and rye in a double blind, placebo controlled food challenge. Bottom:Effect on symptoms of a very strict elimination diet in a patient with atopicdermatitis. Although symptoms decreased initially, they had returned tonormal levels by week 10 (although the diet was still being maintained). If atweek 8 the patient had been given an open challenge or had returned to anormal diet, a food related exacerbation would have been suspected andfalse conclusions drawn. Especially in diseases with a high degree ofspontaneous fluctuations in severity of symptoms a double blind, placebocontrolled food challenge is mandatory, and care must be taken to avoidoverinterpretation of the results

The patient's history should point towardsa close relation between intake of a specificfood or additive and onset of symptoms

The symptoms described by the patient should beof the "classic" atopic type (namely, immediate allergicsymptoms, most often from two or more organs)

Testing may be in vivo or in vitro — skin prick test,specific IgE, basophil histamine release

A restricted, tailor made diet should result in thedisappearance of symptoms (or at least asignificant reduction)

The original symptoms should reappear during challenge;an initial positive open challenge should be confirmedby double blind, placebo controlled food challenge

Case history

Symptoms

Allergy testing

Diagnostic diet

Food challenge

Clinical review



TestingStandardised food extracts are rarely available for use in skinprick testing to diagnose food allergy. However, a few foodextracts have been validated in clinical trials in children andadults by using a double blind, placebo controlled foodchallenge as the gold standard. Foods that have been validatedin this way include cod, peanuts, cows’ milk, hens’ eggs, shrimps,and soy beans. In many cases it is better and more convenient touse fresh fruits for skin prick testing. A drop of liquid food or apiece of solid food is placed on the forearm and prickedthrough (the “prick-prick” method).

The same reservations expressed for skin pricktesting—namely, poorly standardised food allergen extracts—arealso true for the various methods for determining serumconcentrations of allergen-specific IgE against food. Anothermajor problem with the newer and technically highly sensitivemethods is that they detect the many clinically insignificantserological cross reactions, in which IgE raised against anddirected towards epitopes on, for example, grass pollen, alsobinds to wheat proteins, but without any clinical significance ofthe finding.

The significance of reactions to patch testing is currentlybeing evaluated in several centres. However, before any new testis included for routine diagnosis, it should be validated inclinical trials with a double blind, placebo controlled foodchallenge as the gold standard.

Confirmation with oral food challengeDouble blind, placebo controlled food challenge may be neededto confirm the medical history of and positive diagnostic testsfor food allergy. Most published studies show that in an averageof 50% of patients whose medical history plus positive skinprick test result or positive IgE result suggest food allergy,allergy can be confirmed by a double blind, placebo controlledfood challenge. Using fresh foods masked in a vehicle is betterthan using freeze dried foods in capsules. In selected cases anopen challenge (that is, not double blind or placebo controlled)

Results of allergen-specific IgE should beinterpreted with caution, especiallyweakly positive results in patients withhigh serum concentrations of total IgE

Fresh fruit can be used for skin prick testing for fruit allergy

Cross reactivity between birch pollen and apple in patient withspringtime hay fever and oral allergy syndrome after ingestion ofapple

0

10

15

20

25

30

5

Sym

ptom

sco

reSy

mpt

om s

core

0

10

15

20

25

30

5

1 2

Strict elimination diet

Restricted diet Restricted dietOffending foods

3 4 5 6 7 8 9 10Week

Top: Effect on symptoms of introducing restricted diet (elimination ofsuspected offending food) then reintroducing normal diet then returning torestricted diet in a patient who was eventually confirmed as being allergic towheat and rye in a double blind, placebo controlled food challenge. Bottom:Effect on symptoms of a very strict elimination diet in a patient with atopicdermatitis. Although symptoms decreased initially, they had returned tonormal levels by week 10 (although the diet was still being maintained). If atweek 8 the patient had been given an open challenge or had returned to anormal diet, a food related exacerbation would have been suspected andfalse conclusions drawn. Especially in diseases with a high degree ofspontaneous fluctuations in severity of symptoms a double blind, placebocontrolled food challenge is mandatory, and care must be taken to avoidoverinterpretation of the results

The patient's history should point towardsa close relation between intake of a specificfood or additive and onset of symptoms

The symptoms described by the patient should beof the "classic" atopic type (namely, immediate allergicsymptoms, most often from two or more organs)

Testing may be in vivo or in vitro — skin prick test,specific IgE, basophil histamine release

A restricted, tailor made diet should result in thedisappearance of symptoms (or at least asignificant reduction)

The original symptoms should reappear during challenge;an initial positive open challenge should be confirmedby double blind, placebo controlled food challenge

Case history

Symptoms

Allergy testing

Diagnostic diet

Food challenge

Clinical review




ImmunoCAP TestImmunoCAP Test เป็น IgE fluoroenzyme immunoabsorbent assay ระดับของ IgE ที่ตรวจจับได้คือ 0.1 -100 (แต่ threshold levels แค ่0.35) ผลจากการตรวจออกมาเป็นตัวเลขที่มีหน่วยเป็น KUA/I


Oral Food Challenges

Double-blind placebo-controlled food challenge (DBPCFC)

Open food challenge (OFC)

Single-blind placebo-controlled food challenge (SBPCFC)


Treatment

วิธีหลักคือ หลีกเลี่ยงอาหารที่มักทําให้เกิดการแพ้ 8 อย่าง

ในปัจจุบันยังไม่มียาที่ได้รับการรับรองเพื่อรักษาโรคนี้ เนื่องจาก injection immunotherapy (SCIT) ยังไม่มีความปลอดภัยในการใช้ ส่วน oral immunotherapy (OIT) ยังอยู่ในขั้นตอนวิจัยอยู่

ในอเมริกาผู้ที่แพ้อาหารอาจจะพก Epipen Jr. (epinephrine self-injection pens) ติดตัวไว้ในกรณีฉุกเฉิน


EpipenWednesday, February 18, 2009

การป้องกันไม่ให้เกิดอาการแพ้ในเด็กที่มีความเสี่ยงสูง

ให้เด็กกินนมแม่อย่างน้อย 4 – 6 เดือน

ถ้ากินนมแม่ไม่ได้ ให้กินนมที่ทําให้แพ้ได้น้อยใน 4 เดือนแรก

หลีกเลี่ยงอาหารแข็ง และนมวัวใน 4 เดือนแรก


Cross Allergy




การแพ้อาหารมีโอกาสหายได้หรือไม่

การแพ้อาหารสามารถหายได้ โดยเฉพาะผู้ที่แพ้ตั้งแต่วัยเด็ก

ผู้ที่แพ้นม 19% หายแพ้ภายใน 4 ปี 42% หายแพ้ภายใน 8 ปี 64% หายแพ้ภายใน 12 ปี 79% หายแพ้ภายใน 16 ปี

ผู้ที่แพ้ไข่ 4% หายแพ้ภายใน 4 ปี 12% หายแพ้ภายใน 6 ปี 37% หายแพ้ภายใน 10 ปี 68% หายแพ้ภายใน 16 ปี

เด็กกว่า 80% หายแพ้ไข่ตอนเข้าเรียนมหาวิทยาลัย

เด็กทารก 90% ที่แพ้นมและ 50 %ที่แพ้ไข่จะหายแพ้ตอนอายุ 3 ปี แต่ผู้ที่แพ้ถั่วลิสง และปลาค็อดมักจะไม่หายจากการแพ้ แต่อย่างไรก็ตามในผู้ที่แพ้อาหารควรมีการประเมินภาวะทุกปี


Conclusion

Children: milk, eggs, peanuts, soy, wheat

Adults: peanuts, shellfish, nuts, fish

History and physical

Dx by elimination and challenge

Tx avoidance, education, preparation for emergencies

Periodic re-challenge to monitor tolerance


To be continuedFood Allergy II


Health & Medicine

Food allergy slide