• Incidence 0.4 cases per million individuals annually
• Increased hospital incidence of 0.6 cases per 1000 patients
• 400 to 800 deaths annually in the United States

• Pulmonary edema, pulmonary hemorrhage, and pneumothorax
• Laryngeal edema with or without airway obstruction
• Myocardial ischemia and infarction
• Death may result from asphyxiation from upper airway obstruction or profound shock or both.

• Hereditary angioedema
• Systemic mastocytosis
• Pheochromocytoma
• Carcinoid

• Idiopathic
• IgE-mediated
• Non-immunologic mast-cell degranulation
• Exercise-related
• Sulfiting agents
• Non-steroidal anti-inflammatory drug reaction
• Serum sickness

• Vasovagal collapse

• IgE mediated
  • Antibiotics (penicillin and others)
  • Foreign protein agents (bee sting venom, latex antigens, fire ant venom and others)
  • Therapeutic agents (allergen extracts, vaccines and others)
  • Foods (peanuts, nuts, shellfish, and others)
• Non-IgE mediated (activates histamine release from mast cells without IgE)
  • Radiocontrast media
  • Opiates
  • Dextran
  • Vancomycin
  • Polymyxin B
  • Quaternary ammonium muscle relaxants (i.e., methylscopolamine bromide, homatropine methylbromide, methantheline bromide, and probanthine bromide)

Phase 1: Initiate therapy for anaphylaxis. This generally includes: Epinephrine 1:1000 administered subcutaneously, H₁ antihistamines, and H₂ antihistamines (refractory cases).

Phase 2: Attempt to identify the agent that induced the anaphylactic reaction.

Question: How long does it take for a patient to react to an offending allergen?
Significance: Anaphylactic reactions usually begin within seconds to minutes after contact with offending antigen. This can help the physician identify the responsible antigen.

Question: Can a patient have an anaphylactic reaction on their first exposure to an allergen?
Significance: A patient must have had a previous exposure to the offending allergen for sensitization to occur. Therefore, anaphylactic reactions should not occur on first exposure.

Question: What does the patient sense during an anaphylactic reaction?
Significance: Patients commonly describe an impeding doom. This may be the first sign of an impending anaphylactic reaction.

Question: What organ systems are affected in an anaphylactic reaction?
Significance: The target organs may include: the heart, the lungs, the skin and the gastrointestinal tract. Any or all of these target organs may be affected.

Question: What is the mechanism of fatal anaphylaxis?
Significance: Death may occur from upper airway obstruction and/or shock. When treating a patient with anaphylaxis upper airway obstruction, and hypotension should be taken very seriously.

Question: Has the patient had anaphylaxis in the past?
Significance: The patient likely knows the responsible allergen. Efforts should be directed towards allergen avoidance.

Question: Does the patient have autoinjectable epinephrine?
Significance: Most deaths from anaphylaxis are associated with delayed administration of epinephrine. Most patients with a history of anaphylaxis are candidates for autoinjectable epinephrine.

Question: Did the patient experience a bee sting, or are they allergic to any foods?
Significance: Bee venom allergy can result in anaphylaxis. It is important to identify the bee (remember honey bees leave their stinger at the sting site). Immunotherapy is indicated and effective for Bee venom allergic patients. Any food can cause anaphylaxis, but peanuts, nuts, and shellfish are notorious.

Question: Does the patient have asthma or heart disease?
Significance: Asthma and cardiovascular disease are risk factors for death during anaphylaxis.

Question: Does the patient take any medications?
Significance: B-blockers make treatment of anaphylaxis more difficult. Alternative medications should be sought in patients with a history of anaphylaxis.

Finding: Angioedema
Significance: May be noted anywhere during a systemic allergic reaction, but it is much more significant if it involves the lips, tongue, mouth or larynx (can result in airway obstruction).

Finding: Urticaria
Significance: Cutaneous manifestation of a systemic allergic reaction.

Finding: Profuse rhinorrhea
Significance: May signal upper respiratory tract involvement in a systemic allergic reaction.

Finding: Wheezing
Significance: May signal lower respiratory tract involvement in a systemic allergic reaction.

Finding: Tachycardia, and hypotension
Significance: May signal cardiovascular involvement in a systemic allergic reaction. Tachycardia usually represents a compensatory mechanism in order to maintain the patient’s blood pressure.

Test: Plasma histamine
Significance: Plasma histamine is elevated during anaphylaxis.

Test: Serum tryptase
Significance: Serum tryptase becomes elevated during anaphylaxis.

Test: Complete blood count
Significance: Hemoconcentration (as judged by an increased hematocrit or hemoglobin) is common as fluid exits the intravascular space during an anaphylactic reaction.

Test: Chest x-ray
Significance: The bronchospasm associated with anaphylaxis may result in air trapping and hyperinflated lung fields on chest x-ray.

Test: ECG
Significance: Anaphylaxis may show rhythm abnormalities, ischemic changes or infarction on an ECG.

Test: Cardiac enzymes
Significance: Myocardial ischemia during anaphylaxis may result in a myocardial infarction, and elevated cardiac enzymes.

• History of idiopathic anaphylaxis. The allergist can help by testing to likely triggers.
• History of anaphylaxis to bees. Anaphylaxis to bees is an indication for venom desensitization.
• History of food anaphylaxis. The allergist can assist with an appropriate avoidance diet and support resources.
• History of latex anaphylaxis. The allergist can assist with strict latex avoidance precautions, and latex testing if the history is unclear.

• Subcutaneous epinephrine 1:1000 concentration. Early administration of epinephrine is very important.
• Maintain airway. Laryngeal edema can be managed with racemic epinephrine from a meter dose inhaler or nebulizer.
• A tourniquet may be applied (above the injection or sting site) to decrease venous blood return from the site of antigen entry.
• Supplement with oxygen, place in recumbent position and elevate legs. Patients during anaphylaxis have an increased oxygen consumption.
• Diphenhydramine IV. H1 blockade is very important in the control of an anaphylactic reaction.
• Cimetidine IV or Ranitidine IV. H2 blockade may be helpful in refractory anaphylaxis.
• Maintain blood pressure with volume expanders or pressors. Hypotension is a serious manifestation of anaphylaxis.
• Aminophyline may be added for wheezing.
• Hydrocortisone or another systemic steroid should be started. These are most helpful to prevent a late phase reaction, and they are of little help during an immediate anaphylactic reaction.

• All patients who have had anaphylaxis should be discharged with epinephrine in an autoinjecting apparatus.
• Patients with a known trigger should be counseled on strict avoidance.
• All patients should follow up with an allergist.
• Patients not admitted to the hospital should be observed for several hours because late reactions can begin as late as 12 hours after the initial anaphylaxis. These patients are at risk for a second episode of anaphylaxis. These patients, therefore, should be bolused with steroids during the acute treatment, and they should be given a short course of oral corticosteroids to finish at home. In addition, these patients must be discharge with autoinjecting epinephrine (this will provide temporary relief so the patient will have time to seek medical assistance). Patients must know to seek immediate medical help if symptoms return.

Q: When should the autoinjectable epinephrine be used?
A: It is intended for severe allergic reactions as manifested by any of the following: bronchospasm, angioedema of the lips or tongue, or hypotension (dizziness). The patient must seek immediate medical help if the autoinjectable epinephrine is required.

Q: Do patient’s outgrow this condition?
A: No. Subsequent reactions tend to have a more rapid onset, and tend to be more severe.

Q: Who should be referred to an allergist?
A: All patients who have experienced anaphylaxis would benefit from consultation with an allergist. Patients with anaphylaxis from bee stings, and certain antibiotics can be desensitized. In addition, the allergist can be helpful in identifying obscure triggers of anaphylaxis.

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