allergy, anaphylaxis & immune reactions

Allergy, Anaphylaxis & Immune Reactions Christine Kennedy & Katharine Smart

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

Allergy Take Home Points 1. 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

List the 4 types of immune reactions

Type 2 Hypersensitivity

Type 3 Hypersensitivity

List the 8 most common food allergens

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

New onset of “hives”

Mom would like you to refer her for allergy testing.

What do you tell her?

Is this the gold standard?

•Parents present to the ED in distress

•Their 2mo old girl has bloody stools

CMPA=most common food allergy experienced by infants

Hymenoptera

-May reduce the risk of systemic reaction after a subsequent sting from 30-60% to <5 %

-Protection may last for > 20 years

Venom Immunotherapy

Penicillin is the most common cause of drug anaphylaxis

Occurs in 1/5000 - 1/10,000 courses of Penicillin

Vague=rash, GI sx, unknown rxn

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

Convincing = anaphylaxis, angioedema, urticaria, pruritic rash

10% Cross Reactivity??

Retropective cohort of >500,000 patients who received cephaloporins after Penicillin

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

Of the 534,810pts-3920 had an allergic reaction to PCN-624 had an allergic reaction to cephalosporins

Safe to use cephalosporins in pts with reported allergy to pcn

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

• 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)

Common allergic reactions-delayed

List all the Sulfonamide containing drugs you can

Antimicrobials

SulfamethoxazoleSulfasalazine Sulfadiazine Sulfisoxazole

Sulfacetamide

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

Diagnosis?

Allergy Take Home Points 1. 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

Anaphylaxis Take Home Points

1. Epi 1:1000 0.01mg/kg IM in lateral thigh2. Antihistamines may provide relief of

cutaneous symptoms3. 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

What?

Where?

How?

• 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

Antihistamines

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

-Theoretically prevents biphasic reaction

-Onset 4-6h

-IV methylpred 1-2mg/kg [max 125mg]-PO prednisone 1mg/kg [max 75mg]

Non responders

• Epinephrine infusion – 0.1-1mcg/kg/minute

• Vasopressin?

-50 yo M with previous anaphylactic rxn to shellfish

-Presents now with rapidly progressive mucosal edema, SOB, bradycardia & hypotension

PMHx: – IHD, DMII, HTN

He is on an epi infusion and not getting better. Why? What can you do?

Glucagon Dose – 1-5 mg IV (20-30 mcg/kg in peds) over 5 min, then

infusion of 5-15 mcg/min (titrated to response)

Summary of Treatment

1. Epinephrine 0.01 mg/kg IM lat thigh2. Diphenhydramine 1 mg/kg IV [50mg]3. Ranitidine 1mg/kg IV [50 mg]4. Methylprednisone 1-2mg/kg IV [125 mg]5. Epi infusion if persistent hypotension6. Consider: Glucagon if patient on BB7. Consider Ventolin if asthmatic or if patient

continues to struggle

Disposition

• Things to counsel patient/family on– Biphasic Reactions– Epi-pen usage– When to call 911– Medic alert bracelet– Referral to allergist

Biphasic AnaphylaxisHow common?

Who gets it?

3-20% of patients

No validated clinical predictors

Time Frame? 1-72 hours

Biphasic Reaction: Prospective Study

• 20% had biphasic reactions

• Onset 2-38 hours

• Found an association between time to resolution of first episode and chance of recurrence

Biphasic Anaphylaxis Decisions based on judgment not science

• Observation Period– Guidelines (CPS) advise observing for 4-6h

• up to 12h if rural environment– Extra caution with asthmatic patients or pts on BB– Reliable companion is desirable– Consider admitting pts: with severe sx, who req’d repeat epi or

who have biphasic reactions

• Discharge Medications• Epi pen• Corticosteroids

– No clinical trials to support, but little harm in 3d course– There are case reports where it didn’t help

• Antihistamines– No clinical trails to support, may help with cutaneous sx

Common triggers:Foods and NSAIDS pre/post exercise

Anaphylaxis Take Home Points

1. Epi 1:1000 0.01mg/kg IM in lateral thigh2. Antihistamines may provide relief of

cutaneous symptoms3. 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

7 year male

Peri-oral itching after eating an apple

PMHx: Seasonal hay fever, no drug or food allergies

17 month female

17 month female

SERUM SICKNESS

Immune Reaction Take Home Point

1. Need to consider serum sickness in a child with a rash and recent antibiotic use

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