Presentation is loading. Please wait.

Presentation is loading. Please wait.

Consultant in Allergy, Asthma & Immunology

Similar presentations

Presentation on theme: "Consultant in Allergy, Asthma & Immunology"— Presentation transcript:

1 Consultant in Allergy, Asthma & Immunology
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 Co-Chair, Infection/Immunology/Allergy Block, U of Ottawa School of Medicine

2 OBJECTIVES Define allergic and atopic disorders
The Allergic March & the Allergy Epidemic What is a food allergy? How to diagnose food allergies

3 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

4 Allergy testing detects specific IgE to an allergen
Allergy testing detects specific IgE to an allergen. Circulating IgE is measured by serum assays (eg RAST or Unicap)

5 Allergy skin tests detect specific IgE bound to mast cells
Allergy skin tests detect specific IgE bound to mast cells. The allergy skin test does not detect the IgE directly but measures the effect of the mediators released in the skin when the mast cell degranulates in response to allergen exposure during the allergy test

6 Early phase reaction occurs in minutes due to release of pre-formed mediators ( vasoactive amines and proteases eg histamine, tryptase, chymase and heparin; and TNFa) and newly generated mediators eg platelet activating factor, eosinophil chemotactic factor, leukotrienes, TNFa as well, prostaglandins & HETEs, IL 3,4,5 etc). The late phase reaction occurs 4-12 hours later due to recruitment of inflammatory cells to the area by which takes time for the cells to move to the area of inflammation (eosinophils. Neutrophils, TH2 cells)


8 urticaria

9 Childhood asthma : Blame your parents
Both parents asthmatic : % risk One parent asthmatic : % risk One parent & one sibling : % risk No one with asthma : 5–10% risk

10 The Allergy Epidemic Atopic Eczema 10-20% Hay Fever 10-20%
Asthma % Peanut allergy %

11 The Allergic March Atopic eczema onset age 0 - 2 yrs
Food allergy onset age yrs Asthma onset age yrs Allergic rhinitis onset age > 5 yrs

12 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




16 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

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

18 Adverse reactions to food can be sub-divided into…
What is food allergy? Adverse reactions to food can be sub-divided into… Non-toxic Toxic Food intolerance: non allergic (non-immune) reactions Pharmacological reactions Eg, sulphites Food allergy Toxins Eg, salmonella, scrombroid fish IgE-mediated Non-IgE Immediate onset Conditions include: oral allergy syndrome anaphylaxis Delayed onset celiac disease dietary protein enterocolitis Adverse reactions to food can be sub-divided into non-toxic or toxic The term food allergy is used when an adverse reaction is due to an immunologic mechanism. The IgE-antibody is responsible for immediate allergic reactions occurring after eating foods Allergic reactions involving immune cells (T-cells) tend to be delayed reactions, where symptoms first occur 4 to 28 hours after eating the food Non-allergic (non-immune) adverse reactions are termed food intolerance Pharmacological reactions to foods are due to chemicals naturally present in the foods Toxic reactions to food can occur in up to 100% of the population provided a sufficient amount of the food is ingested; they are due to toxins (poisons), e.g., to histamine in scombroid fish or salmonella toxins in foods. Oral Allergy Syndrome A severe pollen allergic reaction dut to common proteins that are found both in pollens and in plants and fruits A form of contact urticaria from ingesting a food (usually fresh fruit) Symptoms confined to lips, mouth and throat including itching of the lips, tongue, roof of mouth and throat, with or without facial swelling Most commonly affects patients who are allergic to pollens Examples of causes of adverse reactions to foods Pharmacologic: Caffeine (jitteriness), tyramine in aged cheese (migraine), alcohol, histamine Toxins: Bacterial food poisoning Intolerance (nonallergic hypersensitivity): lactose intolerance, galactosemia, alcohol Food allergy: IgE mediated: urticaria, angioedema, acute rhinoconjunctivities, acute asthma, anaphylaxis, food-associated, exercise-induced anaphylaxis Not IgE mediated: dermatitis herpetiformis, Celiac disease, Heiner syndrome, food protein induced enteritis, eosinophilic esophagitis Masqueraders of food allergy Auriculotemporal syndrome (facial flush with salivation), gustatory rhinitis, scombroid fish poisoning ___________________________________________ Sicherer and Sampson JACI 2006:117(2);S470-S475; Motala, C. Food Allergy, available at ____________________________________________ Sicherer and Sampson JACI 2006; Food Allergy, available at

19 Features of IgE-mediated food induced allergic reactions
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



22 angioedema

23 Atopic eczema

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 The most severe manifestation of a food allergy

25 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: ) ANAPHYLAXIS Common Less common Peanut Soy Tree Nuts Wheat Fish * Mustard Shellfish: Crustaceans Shellfish: Mollusks Cow’s Milk Sulfites Egg Sesame The top 11 priority food allergens in North America, plus sulfites ( not a food allergen but used in foods and can provoke fatal asthma and anaphylaxis by unknown mechanisms). The original proposal did not include mustard, which was later added in 2011

26 Factors Affecting Food Allergy
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)

27 How much is too much? 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)

28 Threshold Doses: How 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 = to 2mg ( 1/2,000 to 1/250 peanut ) Usual starting dose in challenge studies = 100mg peanut flour ( 1/5 peanut )

29 Can the smell or touch of peanut cause anaphylaxis?
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

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

31 Diagnosis of Food Allergy
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%) (OPTIONAL) It is true that negative skin tests exclude food allergy at > 95%. Negative CAP IgE does not reach 95%. When we look at different probability curve, at 0.35 kUA/L the probability of reacting is often around 20%. __________________________________________ Sampson et al. JACI 2003 31

32 Allergy Skin tests 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 A test which is more specific means that if positive, the test is more likely to indicate clinical disease is less false positives; unfortunately this is also often associated with more false negatives. A test which is more sensitive indicates that it is more likely to detect the greatest number of people with a disease, but is often associated with more false positives ie it may indicate some people have the disease when they do not. Testing on the back is not used as much now as it is more painful, scarier for the patient who cannot see it, and is probably too sensitive

33 Different devices to do prick allergy tests
Different devices to do prick allergy tests. They all introduce the allergen solution in the skin, then wait mins for a localized allergic reacvtion ( a hive)

34 Positive allergy skin test results in a child
Positive allergy skin test results in a child. Cant tell whether he’s happy or sad; but prick testing is only a minor discomfort – the real discomfort is when there is a positive test and you cannot itch it for 15 minutes

Peanut PST > 6mm : ½ will be allergic Peanut PST > 8mm : Most likely allergic Cow’s Milk PST > 8mm : “ “ Egg PST > 7mm : “ “

36 Probability Curve for Peanut
Note that at a Unicap level of 14 kU/L of peanut specific IgE, a patient has a 95% probability of reacting to ingestion of peanut. Note that if the Uniicap is under 0.35 kU/L, in a patient with a previous history of peanut allergy, there is still a 15 – 27% chance of reacting to peanut on ingestion.

37 Food Challenge 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 (OPTIONAL) __________________________________________ Saleh Al-Muhsen et al CMAJ 2003 37

38 Food allergy IgE non-IgE
. Food types 11 priority allergens Milk,soy,wheat Symptoms Skin, respiratory, GI, systemic GI, Failure to thrive, Eczema, anemia, hypo- albuminemia Time to onset of symptoms Acute: minutes to 4 hours Subacute to chronic: days to weeks Duration 4-6 hours Days to weeks FTT – failure to thrive; hypoalbuminemia – low serum albumin, which in food allergy is due to loss of albumin by leakage into the gut due to increased gut permeability from the allergic reaction to foods in the gut.

39 Food allergy IgE non-IgE
Threshold dose Single dose, small amounts eg grams Cumulative doses, usually large exposures Atopic family Yes Variable Antihistamine Rx Usually responds No response Lab Blood eosinophils, elevated IgE Stool mucus, WBC Biopsy-flattened villi, eosinophilia Allergy tests/ Specific IgE Often positive with good clinical correlation Variable-clinical correlation often not as dramatic . Know the differences between these two reactions and also what food intolerance is.

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

41 end

42 ACTIONS OF HISTAMINE Peripheral vasodilation
Increased vascular permeability Altered cardiac conduction Bronchial/intestinal smooth muscle contraction Nerve stimulation-Cutaneous pruritus/pain Increased glandular mucus secretions Pruritus- itch

43 Food Allergy: not just nuts
Young Children Adult Milk 2.5%1 0.3% 1 Egg 1.3% 1 0.2% 1 Peanut 0.8% 1 1.62% 2 0.6% 1 Tree nuts 0.5% 1 Fish 0.1% 1 0.4% 1 Shellfish 2.0% 1 (OPTIONAL SLIDE) The estimated prevalence of peanut allergy is 1.62 as per results of a Canadian follow-up study conducted in Montreal Peanut Peanut has been a leading cause of severe, life-threatening, and even fatal allergic reactions Peanut allergy requires stringent avoidance and management plans as it is one of the most common food allergies in children, adolescents, and adults Milk & egg Many young children outgrow an allergy to milk and egg within the first decade of life, some will continue to remain at risk of anaphylaxis About 2.5% of newborn infants have hypersensitivity reactions to cow milk. About 80% outgrow the allergy by their fifth birthday Fish and shellfish Can be severe and life threatening; therefore, strict avoidance must be practiced Reference: CSACI Guidelines for anaphylaxis in schools and other child care settings. Available at ____________________________________________ H Sampson Food Allergy Update JACI 2004 Ben-Shosham et al, JACI 2009 43

44 Signs and Symptoms: IgE 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

Download ppt "Consultant in Allergy, Asthma & Immunology"

Similar presentations

Ads by Google