Allergy 101. Lori Connors, MD, MEd, FRCPC Allergy and Clinical Immunology. Dalhousie University Mini Medical School Oct 19, 2017

Transcription

1 Allergy 101 Lori Connors, MD, MEd, FRCPC Allergy and Clinical Immunology Dalhousie University Mini Medical School Oct 19, 2017

2 Objectives By the end of this talk participants will be able to: Define allergy Discuss why are allergies increasing Explain allergy testing Describe early introduction of foods Review common allergies

3 Definition of ALLERGY Abnormal, unexpected immune system response to something that is HARMLESS Well defined immunological pathway, mediators involved and symptoms produced Physiologic mechanism is NOT a mystery Why certain ALLERGENS are so ALLERGENIC is still an unknown

4 Type 1 Hypersensitivity

5 Key players IgE and its receptor Mast cells Histamine (and other mediators)

6 Definition of ATOPY Collection of allergic conditions that usually start in childhood: Eczema, Food allergy Allergic rhinitis Asthma Hereditary, mom s genes most important NOT drug allergy, adult onset food allergy, contact dermatitis ( ie, nickel allergy), venom allergy

7 ATOPY 1/3 of the population is ATOPIC Various theories why allergies are increasing Better diagnosis Lifestyle changes Natural selection HYGIENE HYPOTHESIS

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9 Why are allergies increasing?

10 Hygiene hypothesis Epidemiologic observation At birth, mostly a T cell helper 2 population Unless stimulated to switch to T cell helper 1, T cells continue promote atopic disease

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13 FOOD ALLERGY

14 How common is it?

15 Priority Food Allergens in Canada Peanuts Tree nuts Fish Shellfish Wheat Cow s milk Eggs Mustard Soy

16 Priority Food Allergens in Canada Peanuts Tree nuts Fish Shellfish Wheat Cow s milk Eggs Mustard Soy Which is most common? In kids? In adults?

17 What are the symptoms of food allergy?

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20 Definition of Anaphylaxis A serious allergic reaction Rapid in onset May cause death Sampson et al. JACI 2006; 117(2):391-7.

21 Anaphylaxis is Highly Likely When 1 of the Following 3 Criteria Are Fulfilled: 1. Acute onset (minutes to several hours) with involvement of the skin, mucosal tissue, or both (e.g., generalized hives, pruritus or flushing, swollen lips-tongue-vulva) AND AT LEAST ONE OF THE FOLLOWING: respiratory compromise reduced BP or associated symptoms of end-organ dysfunction 2. Two or more of the following that occur rapidly (minutes to several hours) after exposure to a likely allergen for that patient: involvement of the skin/mucosal tissue respiratory compromise reduced BP or associated symptoms persistent gastrointestinal symptoms 3. Reduced BP after exposure to known allergen (minutes to several hours) infants and children: low systolic BP (age specific) or > 30% decrease in systolic BP adults: systolic BP < 90 mm Hg or > 30% decrease from patient s baseline values Sampson et al. JACI 2006; 117(2):391-7.

22 Anaphylaxis is Highly Likely When 1 of the Following 3 Criteria Are Fulfilled: 1. Acute onset (minutes to several hours) with involvement of the skin, mucosal tissue, or both (e.g., generalized hives, pruritus or flushing, swollen lips-tonguevulva) AND AT LEAST ONE OF THE FOLLOWING: respiratory compromise reduced BP or associated symptoms of end-organ dysfunction 2. Two or more of the following that occur rapidly (minutes to several hours) after exposure to a likely allergen for that patient: involvement of the skin/mucosal tissue respiratory compromise reduced BP or associated symptoms persistent gastrointestinal symptoms 3. Reduced BP after exposure to known allergen (minutes to several hours) infants and children: low systolic BP (age specific) or > 30% decrease in systolic BP adults: systolic BP < 90 mm Hg or > 30% decrease from patient s baseline values Sampson et al. JACI 2006; 117(2):391-7.

23 Anaphylaxis is Highly Likely When 1 of the Following 3 Criteria Are Fulfilled: 1. Acute onset (minutes to several hours) with involvement of the skin, mucosal tissue, or both (e.g., generalized hives, pruritus or flushing, swollen lips-tongue-vulva) AND AT LEAST ONE OF THE FOLLOWING: respiratory compromise reduced BP or associated symptoms of end-organ dysfunction 2. Two or more of the following that occur rapidly (minutes to several hours) after exposure to a likely allergen for that patient: involvement of the skin/mucosal tissue respiratory compromise reduced BP or associated symptoms persistent gastrointestinal symptoms 3. Reduced BP after exposure to known allergen (minutes to several hours) infants and children: low systolic BP (age specific) or > 30% decrease in systolic BP adults: systolic BP < 90 mm Hg or > 30% decrease from patient s baseline values Sampson et al. JACI 2006; 117(2):391-7.

24 Treatment??

25 Treatment?? Epinephrine auto-injector EpiPen, Epipen Jr Antihistamines are NOT life-saving Don t delay Epi Go to emerg after Epi

26 Peanut allergy Relatively common, often permanent, and often severe Food allergy prevalence 4-5% in children Peanut allergy Prevalence ~ 6%; has been increasing Prevalence differs around the world North America the highest Asia the lowest Israel very low as well

27 Food allergy Can we prevent food allergies? No good evidence to recommend any dietary practices during pregnancy No good evidence to recommend any delay in introduction of foods, ANY FOOD ANY TIME

28 Prevention of food allergies OLD advice No peanuts in pregnancy LOTS of peanuts in pregnancy Delayed introduction of highly allergenic foods Breast feeding decreases incidence of food allergy

29 Prevention of food allergies CURRENT advice Peanuts ad lib in pregnancy Any food, any time Lots of reasons to breastfeed, but decreasing allergies not proven

30 LEAP Study Learning Early About Peanut allergies

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33 Original Article Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy George Du Toit, M.B., B.Ch., Graham Roberts, D.M., Peter H. Sayre, M.D., Ph.D., Henry T. Bahnson, M.P.H., Suzana Radulovic, M.D., Alexandra F. Santos, M.D., Helen A. Brough, M.B., B.S., Deborah Phippard, Ph.D., Monica Basting, M.A., Mary Feeney, M.Sc., R.D., Victor Turcanu, M.D., Ph.D., Michelle L. Sever, M.S.P.H., Ph.D., Margarita Gomez Lorenzo, M.D., Marshall Plaut, M.D., and Gideon Lack, M.B., B.Ch., for the LEAP Study Team N Engl J Med Volume 372(9): February 26, 2015

34 Study Overview Children 4 to 11 months of age who were at high risk for development of peanut allergy were assigned to consumption or avoidance of peanuts until 60 months of age. Peanut allergy was more than five times as likely to develop in children assigned to peanut avoidance.

35 Learning Early About Peanut Allergy (LEAP Study) Screening Randomisation/ Stratification Intervention group Peanut consumed 3 times per week(n 320) 4-11 month old children eczema and/or egg allergy Control Group Peanut avoidance (n 320) 4-11 months 1 yr 2.5 yr 5 yr V -1 V 0 V 12 V 30 V 60

36 86.1% relative reduction 70.0% relative reduction The study had a 98.4% retention rate! Du Toit et al, NEJM, 2015

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38 Early OIT 40 children, age 9-36 months Randomized to 300 or 3000 mg maintenance dose, compared with 154 matched controls Primary goal was SU at 4 weeks 85% of low dose group 71% of high dose group Treated children 19x more likely to successfully consume dietary peanut than controls Vickery et al, JACI 2016, epub

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40 NIAID Addendum Guidelines for the Prevention of Peanut Allergy Guideline Infant Criteria Recommendations Earliest Age of Peanut Introduction 1 Severe Eczema and/or Egg Allergy 2 Mild to Moderate Eczema 3 No eczema or food allergy Strongly consider evaluation by sige and/or SPT, and if necessary oral food challenge. Based on test results, introduce peanut. Introduce peanutcontaining foods Introduce peanutcontaining foods 4 to 6 months Around 6 months Age appropriate, in accordance with family preferences and cultural practices

41 Bottom Line? Introduce highly allergenic foods early! Unless babe has moderate to severe eczema Early= 4 to 6 months Once food is in diet, keep it in!

42 Allergy Testing Skin Prick Testing Serum specific IgE (ImmunoCAP) Oral Challenges (Patch testing)

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44 Allergy Testing Epicutaneous skin testing Sensitivity 90% Specificity 50% Safe way to introduce allergen and demonstrate allergic sensitization Quick, easy, can be done in an office setting Can be done at any age, presuming they have demonstrated potentially allergic symptoms

45 Food allergy testing Predicts for ALLERGIC, IgE mediated, histamine mediated reactions ONLY Ie, NOT GI intolerance symptoms, headaches, acne, fatigue, etc Random food allergy testing is generally NEVER indicated. Only implicated foods are tested

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47 Inhalant Allergens Indoor allergens: house dust mite, animals, molds Outdoor allergens: tree, grass, and weed pollen, molds. Occupational allergens: baker s asthma, farmer s lung, shellfish workers, veterinarians, etc.

48 Allergen avoidance is first line therapy Animals Removal from home is ideal Keeping animal out of the bedroom, removal of carpet, mattress covers and HEPA filters are the next best thing Washing the animal, twice a week

49 Do hypoallergenic animals exist? NO! Several studies showing no difference in breed allergenicity, ie poodle versus golden retriever One study measured dog dander levels in home with hypoallergenic dogs versus non-hypoallergenic dogs, and there was no difference

50 Animal allergy Other contributing factors: Accumulation of animal allergen Carpeting, upholstered furniture Other allergens/irritants in environment Some degree of desensitization to OWN pet, but not others, beware of THANKSGIVING EFFECT Desensitization/immunotherapy/allergy shots available

51 Venom allergy

52 Venom allergy

53 Venom allergy First attributable death to stinging insect was in 2641BC as seen on the walls of King Menes tomb. Earliest medical reference was in 1925, a report by Braun.

54 Epidemiology Prevalence of severe reactions % deaths per year in the US most rxns in age age<20, but more deaths in older population

55 CLASSIFICATION OF REACTION Normal--local pain, redness, swelling Large Local Reactions--more pronounced pain, swelling, redness, often peaks in 48h and can last a week. Swelling is continuous with the site of sting.

56 CLASSIFICATION OF REACTION MILD Systemic--Swelling away from the sting site, generalized skin eruption, no involvement of resp, GI or CVS compromise SEVERE Systemic--As above, with any one or more organ involvement

57 RISK OF FURTHER REACTION Risk of systemic reaction Normal 1-2% Large local <5% Mild systemic <16y 10% >16y 30-60% Severe systemic 60%

58 TESTING Confirms the diagnosis Identifies the culprit Guides immunotherapy

59 IMMUNOTHERAPY Desensitize to the equivalent of twice the amount of a typical sting ug of venom extract. Maintain for a maximum of 5 years

60 IMMUNOTHERAPY Venom immunotherapy is the most effective immunotherapy that an Allergist administers. When sting challenged, % protection rate in adult and children after 3 months of treatment (Valentine MD, NEJM, 1990)

61 How not to get stung Be careful when outdoors in the summer, esp early fall. Wear shoes. Don t smell and look like a flower. Don t drink out of a can. Have hives removed professionally. Insect repellant not protective.

62 Other insects Not considered to be IgE mediated allergenic Large local reactions are common and treated symptomatically only Rarely, systemic reactions are documented

63 Objectives By the end of this talk participants will be able to: Define allergy Discuss why are allergies increasing Explain allergy testing Describe early introduction of foods Review common allergies

64 QUESTIONS???