Allergic Reaction
Aka: Allergic Reaction, Anaphylaxis

  1. See Also
    1. Urticaria
  2. Causes: Common
    1. Idiopathic
    2. Hymenoptera Allergy (e.g. bees, wasps)
      1. Results in >50 fatal U.S. reactions per year
    3. Food Allergy (30% of anaphylactic episodes)
      1. Cow's Milk
      2. Egg whites
      3. Fish
      4. Peanuts
      5. Shellfish
    4. Medications
      1. Penicillin Allergy (75% of anaphylactic deaths)
      2. NSAIDs or Aspirin
      3. Radiographic Intravenous Contrast Material
    5. Allergic Contact Dermatitis
      1. Latex Allergy
  3. Signs: Mild
    1. General
      1. Feeling impending doom
      2. Pruritus (uncommon without rash)
      3. Metallic Taste in mouth
    2. Naso-ocular
      1. Itchy nose or eyes
      2. Sneezing
      3. Clear, watery Eye Discharge or Nasal discharge
    3. Skin (occurs)
      1. Urticaria: Hives
      2. Angioedema: Facial swelling and Lip swelling
  4. Signs: Moderate
    1. Neurologic
      1. Dizziness
      2. Weakness
    2. Gastrointestinal
      1. Nausea, Vomiting
      2. Bloody Diarrhea
      3. Abdominal Pain
      4. Fecal urgency or Incontinence
    3. Genitourinary
      1. Uterine cramps
      2. Urinary urgency or Incontinence
  5. Signs: Severe
    1. Neurologic
      1. Syncope
      2. Seizures
    2. Respiratory: Angioedema of upper airway
      1. Hoarseness
      2. Dysphonia
      3. Lump in throat
      4. Bronchospasm
      5. Stridor or Wheezing
      6. Dyspnea and Tachypnea
    3. Cardiovascular
      1. Hypotension
      2. Arrhythmia
      3. Tachycardia
  6. Differential Diagnosis
    1. Hypovolemic, cardiogenic, neurogenic or septic shock
    2. See Flushing
    3. See Wheezing
    4. Panic Attacks
    5. Systemic mastocytosis
    6. Leukemia
    7. Hereditary Angioedema
  7. Management: Emergency Department
    1. General Measures
      1. ABC Management
      2. Oxygen
      3. Intravenous Fluids
      4. Nebulized Beta-Agonist (Albuterol)
    2. Anaphylaxis with Airway Compromise
      1. Epinephrine (1:1000 concentration = 1 mg/ml)
        1. Intramuscular dosing preferred over subcutaneous
        2. Repeat every 10 to 15 minutes prn up to 3 doses
        3. Cardiac monitoring required for repeat dosing
        4. Adult: 0.3-0.5 cc (0.3 to 0.5 mg) SC or IM
        5. Child: 0.01 ml/kg SC or IM (up to 0.3 ml)
      2. Unresponsive to Epinephrine
        1. Glucagon 1 mg IV if patient uses Beta-Blockers
        2. Norepinephrine may also be considered
    3. Urticaria, Pruritus or Flushing
      1. Diphenhydramine (Benadryl) every 6 hours prn
        1. Adult: 25-50 mg IM/IV
        2. Child: 1.25 mg/kg IM/IV
    4. Hypotension (due to vasodilitation and third spacing)
      1. Fluid Resuscitation with isotonic saline (NS, LR)
        1. Large volumes may be required
      2. Pressors (e.g. Dopamine) may be required
      3. Consider Epinephrine by continuous IV infusion
    5. Respiratory distress
      1. Nebulized Beta adrenergic agonist (e.g. Albuterol)
      2. Consider Endotracheal Intubation
      3. Consider aminophylline 5.6 mg/kg IV load over 20 min
    6. Severe or persistent symptoms not resolved in 30 min
      1. Hydrocortisone 5 mg/kg IV
      2. Methylprednisolone (Solu-Medrol) every 6 hours
        1. Adult: 60-125 mg IV/IM
        2. Child: 0.5-1 mg/kg IV/IM
  8. Disposition
    1. Observation of moderate to severe reactions for 6 hours
      1. Minimum observation time is 3 hours
      2. Prolonged reaction may require 24 hour observation
    2. Biphasic reactions occur several hours later in 20%
  9. Management: Home
    1. Diphenhydramine (Benadryl)
      1. Adult: 25-50 mg PO q6h x3 days
      2. Child: 5 mg/kg/day PO divided q6h
    2. Prednisone
      1. Corticosteroids most effective if started early
        1. Administer within 1-2 hours if possible
      2. Adult: 60 mg PO qd x3 days
      3. Child: 0.5-1 mg/kg/dose PO qd x3 days
    3. Cimetidine (Tagamet)
      1. Adult: 400 mg PO bid x3 days
  10. Prevention
    1. Medical Alert Bracelet should be worn
    2. Strict avoidance of allergen
    3. Epinephrine Home Injectable Devices (e.g. EpiPen)
    4. Consider Skin Testing and Desensitization therapy
      1. Indicated if re-exposure is likely or unavoidable
  11. References
    1. Ellis (2003) CMAJ 169(4):307-11
    2. Sampson (2003) Pediatrics 111:1601-8
    3. Tang (2003) Am Fam Physician 68:1325-40
anaphylaxis (C0002792)
Definition (MSH) An acute hypersensitivity reaction due to exposure to a previously encountered ANTIGEN. The reaction may include rapidly progressing URTICARIA, respiratory distress, vascular collapse, systemic SHOCK, and death.
Definition (CSP) a manifestation of immediate hypersensitivity in which exposure of a sensitized individual to a specific antigen or hapten results in urticaria, pruritis and angioedema, followed by vascular collapse and shock often accompanied by life threatening respiratory distress.
Definition (NCI) Systemic anaphylaxis is the most dramatic example of an immediate hypersensitivity reaction; is uncommon and unexpected in nature and occasionally results in a fatal outcome.
Definition (NCI) Pertaining to anaphylaxis.
Definition (GO) OBSOLETE. Extreme immunological sensitivity of the body or tissues to the reintroduction of an antigen. It is a form of anamnestic reaction and is accompanied by pathological changes in tissues or organs due to the release of pharmacologically active substances. [ISBN:0198506732 "Oxford Dictionary of Biochemistry and Molecular Biology"]
Concepts Pathologic Function (T046)
MSH D000707
English Allergic shock, Anaphylactic Reaction, Anaphylactic Reactions, anaphylactic shock, anaphylaxis, Generalised anaphylaxis, Generalized anaphylaxis, Systemic anaphylaxis
Spanish anafilaxia, anafilaxia generalizada, anafilaxia sistemica, anafilaxis, choque anafilactico, reaccion anafilactica, shock anafilactico
Parent Concepts Immediate hypersensitivity (C0020523), Transfusion Adverse Reaction (C1547889), Shock (C0036974), Acute allergic reaction (C0413234), Reason not stated concept (C1276325), Duplicate concept (C1274013)
Sources AOD , COSTAR, CSP, CST, DXP, GO, HL7V2.5, LCH, MEDLINEPLUS, MSH, MTH, NCI, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)
Hypersensitivity (C0020517)
Definition (MSH) Altered reactivity to an antigen, which can result in pathologic reactions upon subsequent exposure to that particular antigen.
Definition (CSP) state of previously immunized body in which tissue damage results from the immune response to a further dose of antigen.
Definition (HL7V3.0) <p>Hypersensitivity to an agent caused by an immunologic response to an initial exposure</p>
Definition (NCI) Hypersensitivity; a local or general reaction of an organism following contact with a specific allergen to which it has been previously exposed and to which it has become sensitized.
Definition (NCI) An exaggerated response by the immune system to a drug or other substance.
Definition (GO) An inflammatory response to an exogenous environmental antigen or an endogenous antigen initiated by the adaptive immune system. [GOC:jal, ISBN:0781735149 "Fundamental Immunology"]
Definition (NCI) Hypersensitivity; a local or general reaction of an organism following contact with a specific allergen to which it has been previously exposed and to which it has become sensitized.
Concepts Pathologic Function (T046)
ICD9 995.3
MSH D006967
English Allergic disorder, Allergic reaction, Allergic state, ALLERGIC/HYPERSENSITIVITY, Allergies, Allergy, Allergy disorder, Atopic AND/OR hypersensitivity state, Disorder due to allergic reaction, Disorder due to immune hypersensitivity reaction, Hypersensitivities, Hypersensitivity, Hypersensitivity reaction, HYSN, Immune hypersensitivity disorder, Immune hypersensitivity reaction
Spanish alergia, estado alergico, estado atopico Y/O de hipersensibilidad, hipersensibilidad, reaccion de hipersensibilidad, reaccion por hipersensibilidad inmunologica, trastorno alergico, trastorno causado por reaccion alergica, trastorno de hpersensibilidad inmunologica, trastorno debido a reaccion alergica, trastorno inmunologico por hipersensibilidad, trastorno por reaccion alergica, trastorno por reaccion inmunologica por hipersensibilidad
Parent Concepts manifestations of immunopathology (C1609432), Pathologic Processes (C0030660), acute inflammatory response to antigenic stimulus (C1817888), intolerance to substance (C1744706), Immune System Diseases (C0021053), Hypersensitivity (C0020517), Mechanism (attribute) (C0441712), Adverse reactions (C0559546), Ambiguous concept (C1274012), Duplicate concept (C1274013), Propensity to adverse reactions (C1628518), Hypersensitivity disorder (C1719883)
Sources AOD , COSTAR, CSP, CST, GO, HL7V3.0, MEDLINEPLUS, MSH, MTH, MTHICD9, NCI, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)

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