Allergy, Anaphylaxis & Immune Reactions

1. Allergy, Anaphylaxis & Immune Reactions Christine Kennedy & Katharine Smart

2. Objectives • Need to cover the basics • Definition of anaphylaxis • Types of immune reactions • Discuss the following allergies: • antibiotic, venom & Cow’s Milk Protein • Review the evidence for anaphylaxis meds • Demonstrate how to use an epi pen • Review Serum Sickness

3. Allergy Take Home Points • There are 4 types of immune reactions. Type 1 is IgE mediated (ie causes anaphylaxis) 2. Cow’s milk protein allergy is the most common infant “allergy” 3. Patients with venom allergies should be referred for venom immunotherapy 4. True antibiotic allergies occur infrequently -Patients with suspected PCN allergy should be referred for skin testing -Cephalosporins can generally be safely used in pts with PCN allergies

4. List the 4 types of immune reactions

6. Type 2 Hypersensitivity

7. Type 3 Hypersensitivity

9. List the 8 most common food allergens

10. True or False? • If you delay the introduction of certain foods (ie peanuts) you will decrease the likelihood that a child will have an allergy • If a Mom avoids certain foods in pregnancy, she will decrease the chance of her child developing an allergy • If a sibling has a food allergy, the other sibling has an increased chance of having the allergy • If someone “smells” an allergen, they can have a reaction

11. New onset of “hives” Mom would like you to refer her for allergy testing. What do you tell her?

12. Is this the gold standard?

13. Parents present to the ED in distress • Their 2mo old girl has bloody stools

14. CMPA=most common food allergy experienced by infants

16. Hymenoptera

17. Venom Immunotherapy -May reduce the risk of systemic reaction after a subsequent sting from 30-60% to <5 % -Protection may last for > 20 years

19. Penicillin is the most common cause of drug anaphylaxis Occurs in 1/5000 - 1/10,000 courses of Penicillin

20. Vague=rash, GI sx, unknown rxn Convincing = anaphylaxis, angioedema, urticaria, pruritic rash • 33% of patients with a + skin test reported a vague history of a penicillin reaction • Take home message: Patients with vague histories should undergo PCN skin testing, just as patients with more convincing histories, prior to repeat doses of PCN

21. 10% Cross Reactivity??

22. Safe to use cephalosporins in pts with reported allergy to pcn Retropective cohort of >500,000 patients who received cephaloporins after Penicillin Of the 534,810pts -3920 had an allergic reaction to PCN -624 had an allergic reaction to cephalosporins 25 had anaphylaxis with Penicillin (25/3920, 0.64%) 1/25 had a second anaphylactic reaction with a cephalosporin • Allergic events with cephalosporins are increased with hx of rxn to penicillin but to a similar degree as those who have had rxns to SMX • -unlikely that rxns are a class effect

23. Endorse the use of cephalosporins for patients with penicillin allergies • As long as the reaction isn’t severe

24. No good evidence to support cross reactivity between PCN’s and cephalosporins based on class effect alone • Patients with a true anaphylactic history to penicillin are at risk of reacting to other abx, not just cephalosporins • Patients with asthma generally have poorer outcomes • As Emerg docs we have the advantage of being able to treat adverse reactions quickly (If in doubt, observe post 1st dose)

26. Common allergic reactions-delayed

27. List all the Sulfonamide containing drugs you can

28. Antimicrobials • Sulfamethoxazole • Sulfasalazine Sulfadiazine Sulfisoxazole Sulfacetamide

30. Sulfa Antimicrobial Allergies 8% of patients treated with SMX have an adverse reaction • 3% of reactions represent hypersensitivity Largest % abx induced cases of TEN and SJS

31. Diagnosis?

32. Allergy Take Home Points • There are 4 types of immune reactions. Type 1 is IgE mediated (ie causes anaphylaxis) 2. Cow’s milk protein allergy is the most common infant “allergy” 3. Patients with venom allergies should be referred for venom immunotherapy 4. True antibiotic allergies occur infrequently -Patients with suspected PCN allergy should be referred for skin testing -Cephalosporins can generally be safely used in pts with PCN allergies

35. Anaphylaxis Take Home Points 1. Epi 1:1000 0.01mg/kg IM in lateral thigh 2. Antihistamines may provide relief of cutaneous symptoms 3. Biphasic reactions do occur and recommendation stands that pts should be observed for 4-6 hours 4. Know how to counsel patient/family on epi pen use

40. What? Where? How?

41. Failure to administer epinephrine early is the single most important risk factor for fatal or near fatal reactions • Bock, SA J. Allergy Clin Immunol 2001;107:191-3 • “There are no contraindications to the use of epinephrine for a life-threatening allergic reaction” • AAAAI board of Directors JACI 1998;102:173-76

43. Antihistamines

46. Antihistamines: Bottom Line • Should not replace epinephrine in the management of anaphylaxis • May alleviate dermatologic symptoms • May play a role in secondary prevention before exposure

47. -Theoretically prevents biphasic reaction • -Onset 4-6h • -IV methylpred 1-2mg/kg [max 125mg] • -PO prednisone 1mg/kg [max 75mg]

50. Non responders • Epinephrine infusion • 0.1-1mcg/kg/minute • Vasopressin?