Allergy

Last updated 07/19/2017 - Written by Melissa Stone MD

Types of Allergic Reactions
-          Type 1: IgE mediated: ex. anaphylaxis, asthma, eczema, allergic rhinitis
-          Type 2: Antibody mediated: ex. hemolytic anemia, Graves disease
-          Type 3: Immune complex deposition: ex. glomerulonephritis, SLE, RA
-          Type 4: Delayed hypersensitivity: contact dermatitis, chronic rejection
-          Anaphylactoid: not IgE mediated: ex. contrast media reaction

Allergy Testing
1.      Allergen-specific serum IgE (formerly known as RAST testing)
-          Can be ordered to specific environmental or food allergens
-          Allergy, Northeast Screen Panel tests for common environmental allergen
-          Only order for foods with clinical history consistent with reaction
2.      Skin prick testing (SPT)
-          Performed in AI clinic to common environmental or food allergens
3.      Patch testing
-          Performed in AI clinic with specially ordered patches usually for contact reactions to skin and hair products
4.      Challenge
-          Performed in AI clinic under supervision typically with food allergens
5.      Advanced testing
-          Hereditary angioedema work-up: Tryptase, C1 Esterase Inhibitor, C1 Esterase Inhibitor Functional, C4 Complement Component, Complement Component C1q
6.      Pearls
-          Environmental testing is typically not performed until 4 years of age
-          No anti-histamines for at least 1 week prior to SPT/Patch/Challenge
-          Common food allergens: peanuts, tree nuts, shellfish, fish, milk, soy, wheat, egg

Allergic Reaction Treatment
1.      Medical: anti-histamines, steroids, epinephrine
2.      Subcutaneous immunotherapy: common for environmental allergens, can be used for insect reactions, clinical trials for food allergens (not currently done at CHAM)
3.      Avoiding known allergens

Prescribing an EpiPen
-          Prescribe an EpiPen for patients with a history of anaphylaxis or suspected food allergy until can be evaluated by AI
-          Ask every patient with a history of severe allergic reaction at every clinical encounter if they have an unexpired EpiPen and know how to use it
-          Epinephrine dosing for anaphylaxis is 0.01 mg/kg epinephrine 1:1,000
-          EpiPen (0.3 mg for patients over 30 kg)
-          EpiPen Jr (0.15 mg for patients under 30 kg)
-          EpiPen 2-Pak cartons come with 2 EpiPens, each is single use
-          Go to the EpiPen.com website “About EpiPen” to watch a video on how to use an EpiPen; have patients watch the video and/or show them with a trainer
-          Instruct patients to always call 911 if using an EpiPen
-          Instruct patients that if not sure whether or not to use an EpiPen to use it
-          Instruct patients that an EpiPen lasts for 1 year but using an expired EpiPen is not harmful and should be used instead of no EpiPen
-          Instruct patients to always carry EpiPen with them and to have one at school

Drug Allergy
1.      History
-          Severity of reaction (urticaria, angioedema, anaphylaxis)
-          Timing of reaction relative to intake of medication
2.      Treatment
-          All patients with history of drug allergy should be evaluated by AI as an outpatient when healthy as many reported drug allergies are false/outgrown
-          Drug desensitization procedures can be done with AI

Contrast Media Administration
1.      Clarify all allergies prior to administering IV (not PO) CT/MRI contrast
2.      If patient has prior history of severe reaction to anything, pre-medicate
-          Protocol found: intranet, Clinical Dept, Radiology, Pediatric Radiology
3.      If patient is currently having an asthma exacerbation, pre-mediate as well

Resources for Families
-          www.foodallergy.org