The physician s perspective on food allergy nutrition exchange june 2 2011
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THE PHYSICIAN’S PERSPECTIVE ON FOOD ALLERGY NUTRITION EXCHANGE June 2, 2011. Antony Ham Pong MBBS Consultant in Allergy, Asthma & Immunology Clinical lecturer, Pediatrics, Univ of Ottawa; Consultant, Chest Clinic, CHEO

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The physician s perspective on food allergy nutrition exchange june 2 2011

THE PHYSICIAN’S PERSPECTIVE ON FOOD ALLERGYNUTRITION EXCHANGEJune 2, 2011

Antony Ham Pong MBBS

Consultant in Allergy, Asthma & Immunology

Clinical lecturer, Pediatrics, Univ of Ottawa;

Consultant, Chest Clinic, CHEO

Co-Chair, Infection/Immunology/Allergy Block, U of Ottawa School of Medicine


Objectives
OBJECTIVES

  • Define allergic and atopic disorders

  • The Allergic March & the Allergy Epidemic

  • What is a food allergy?

  • How to diagnose food allergies


Atopy allergy
ATOPY & ALLERGY

  • ATOPY is the genetic predisposition to produce IgE on allergen exposure, resulting from an imbalance between TH1 and TH2 helper lymphocytes

  • Specific IgE produced attaches to the surface of mast cells

  • Subsequent allergen exposure causes mast cell inflammatory mediator release

  • ALLERGY is the clinical hypersensitivity which occurs as a manifestation of atopy


Childhood asthma blame your parents
Childhood asthma : Blame your parents

  • Both parents asthmatic : 75% risk

  • One parent asthmatic : 30% risk

  • One parent & one sibling : 40% risk

  • No one with asthma : 5–10% risk


The allergy epidemic
The Allergy Epidemic

  • Atopic Eczema 10-20%

  • Hay Fever 10-20%

  • Asthma 12-20%

  • Peanut allergy 1.62%


The allergic march
The Allergic March

  • Atopic eczema onset age 0 - 2 yrs

  • Food allergy onset age 0 - 2 yrs

  • Asthma onset age 2 - 5 yrs

  • Allergic rhinitis onset age > 5 yrs


The allergy epidemic1
The Allergy Epidemic

  • The Hygiene Theory proposes that the major increase in allergies, which is seen only in well-developed countries, is due to excess cleanliness. Our immune system does not have enough work to do, therefore it begins to react to harmless things in our environment, causing allergies.

  • This may explain in part why 70% of allergic children have no family history of atopic disease


Microbial exposures associated with less allergy and asthma clinical studies
Microbial exposures associated with less allergy and asthma: Clinical studies

  • Older siblings / large family size

  • Early day care

  • Less antibiotic use

  • Lactobacillus ingestion

  • Infections

    • Respiratory tract: measles, tuberculosis, tuberculin positivity

    • Gastrointestinal : Hep A, H. pylori,

  • Being brought up on a farm

    • Animal exposure / Stables exposure

    • Drinking unpasteurized milk ( higher endotoxin levels)

    • Endotoxin levels higher

  • Keeping a dog/cat ( unless one is allergic to it!)

    • Home environment contaminated with endotoxin


Timing is everything

Timing is everything Clinical studies

Genetics ,timing and degree of exposure to irritants, microbes and allergens will determine whether allergic sensitization or tolerance will develop


What is food allergy
What is food allergy? Clinical studies

____________________________________________

Sicherer and Sampson JACI 2006; Food Allergy, available at www.worldallergy.org


Features of ige mediated food induced allergic reactions
Features of IgE-mediated food induced allergic reactions Clinical studies

  • Onset within 30 mins, rarely up to 4 hrs

  • Duration < 4-6 hours

  • Reactions recur reliably with re-exposure

  • Threshold dose (usually small amount)

  • Anaphylaxis can occur with a small amount of a potent allergen or a larger amount of a ‘milder’ allergen


Anaphylaxis overview
ANAPHYLAXIS: OVERVIEW Clinical studies

  • Anaphylaxis is a severe, potentially fatal systemic allergic reaction that occurs suddenly (minutes to hours) after contact with an allergy-causing substance

  • Death can occur in minutes, usually due to closure of airways

  • Allergic reaction affects many body systems : rash & swelling, breathing difficulties, vomiting & diarrhoea, heart failure & low blood pressure  ANAPHYLACTIC SHOCK


Common allergenic foods and their labeling in canada a review
Common Allergenic Foods and their Labeling in Canada – A Review

(Zarkadas M., Scott F, Salminen J, Ham Pong AJ.

Can J Allergy Clin Immunol 1999, 4: 118-141)

ANAPHYLAXIS

Common Less common

Peanut Soy

Tree Nuts Wheat

Fish * Mustard

Shellfish: Crustaceans Shellfish: Mollusks

Cow’s Milk Sulfites

Egg

Sesame


Factors affecting food allergy
Factors Affecting Food Allergy Review

Early Dietary Exposure & Food Allergy Prevalence

Peanut North America

Rice E. Asia esp. Japan

Fish Scandinavia

Sesame Israel

Chickpea India

Wheat America, Europe

Edible Bird’s Nest Singapore

(dried cave swallow saliva)


How much is too much
How much is too much? Review

  • MILK – fatality from 2.5ml ( ½ tsp)

  • EGG – anaphylaxis from 10mg (1/3,000 oz)

  • FISH - anaphylaxis from 1 gm (1/30 0z)

  • SHRIMP – anaphylaxis from 1 gm (1/4 shrimp)


Threshold doses how much peanut is too much
Threshold Doses: ReviewHow much peanut is too much?

  • Dose of peanut causing a subjective reaction eg itchy mouth = 10 ug or 1/50,000 peanut

  • Objective reaction in challenge studies = 0.25 to 2mg ( 1/2,000 to 1/250 peanut )

  • Usual starting dose in challenge studies = 100mg peanut flour ( 1/5 peanut )


Can the smell or touch of peanut cause anaphylaxis
Can the smell or touch of peanut cause anaphylaxis? Review

  • Possibility that high level peanut dust can provoke anaphylaxis in airplanes ( Sicherer 1999)

  • Smell of peanut butter does not cause allergic reactions– reactions to this are most likely due to intense dislike of the smell ( the smell is due to volatile organic molecules and not allergenic proteins), or inadvertent ingestion

  • Anaphylaxis has been induced inhalation of steam carrying food particles eg shrimp, fish, milk


Food allergy route of exposure
FOOD ALLERGY : ROUTE OF EXPOSURE Review

  • Ingestion – directly or indirectly (eg maternal dietary proteins via breast mlk)

  • Inhalation eg boiling foods (eg shrimp, milk), food dust (eg peanut, egg, wheat, psyllium), ?milk contaminated lactose in asthma dry powder inhalers

  • Musosal contact : eye (eg shrimp), rectal (eg milk enema)

  • Skin : abraded skin eg milk containing ointment or lactobacillus capsules; egg lecithin containing creams

  • Parenteral : drug & intralipid formulations


Diagnosis of food allergy
Diagnosis of Food Allergy Review

Positive Allergy Skin Prick Test (SPT) or blood test (CAP IgE)

Indicates presence of IgE antibody NOT clinical reactivity

Must be interpreted in the context of clinical history

Negative SPT and CAP IgE

Essentially excludes IgE antibody (>95%)

__________________________________________

Sampson et al. JACI 2003


Allergy skin tests
Allergy Skin tests Review

  • Prick/puncture – most common technique, introduces allergen into the very superficial skin (epicutaneous layer) usually flexor surface of forearm, sometimes on back; is more specific but not as sensitive as intradermal

  • Intradermal – introduces a larger quantity of allergen into a deeper layer of skin of upper forearm; more sensitive but less specific than prick

  • Scratch – old technique, not used now as too variable


Allergy prick skin test size does matter

ALLERGY PRICK SKIN TEST “SIZE DOES MATTER” Review

Peanut PST > 6mm : ½ will be allergic

Peanut PST > 8mm : Most likely allergic

Cow’s Milk PST > 8mm : “ “

Egg PST > 7mm : “ “



Food challenge
Food Challenge Review

  • Reasons to challenge:

    • Confirm reactivity

    • Confirm non-reactivity

    • Follow for tolerance

  • Oral challenge testing (MD supervised, ER meds available)

    • Open

    • Single-blind

    • Double-blind, placebo-controlled (DBPCFC)

      • Sensitivity, Specificity, PPV, NPV ~ 100%

  • Limitations:

    • Risk to patient

    • Dose

    • Duration of challenge

    • Success of blinding

__________________________________________

Saleh Al-Muhsen et al CMAJ 2003


Food allergy ige non ige
Food allergy ReviewIgE non-IgE

.


Food allergy ige non ige1
Food allergy ReviewIgE non-IgE

.


Food allergy prognosis
FOOD ALLERGY PROGNOSIS Review

  • Onset before age 3 years esp cow’s milk (age 2-3), egg(age 5-7), soy & wheat (age 2-3) : usu outgrown

  • Onset after age 3 years : usu lifelong

  • Peanut allergy : up to 20% reported to be outgrown ( probably optimistic)

  • Usually lifelong : Peanut, tree nuts, fish, shellfish, seeds



Actions of histamine
ACTIONS OF HISTAMINE Review

  • Peripheral vasodilation

  • Increased vascular permeability

  • Altered cardiac conduction

  • Bronchial/intestinal smooth muscle contraction

  • Nerve stimulation-Cutaneous pruritus/pain

  • Increased glandular mucus secretions


Signs and symptoms ige vs non ige
Signs and Symptoms: ReviewIgE vs Non-IgE

IgE Non-IgE

Skin

Urticaria

Angioedema

Atopic dermatitis

Respiratory

Throat tightness

Rhinitis

Asthma

Gut

Vomit

Diarrhea

Pain

Anaphylaxis

____________________________________________

Sicherer and Sampson JACI 2006; Sampson JACI 2003


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