Anaphylaxis

Angioedema2010[1]

Anaphylaxis is a rapidly progressing, life-threatening allergic reaction.


Presentation

The symptoms of anaphylaxis usually occur within minutes of exposure to an allergen. Symptoms usually vary in severity. Sometimes they only cause mild itching or swelling, but in some people they can be severe and life threatening [8].

The symptoms of anaphylaxis include itchy skin with red, raised rashes known as hives. There may be urticaria, angioedema and flushing.

The respiratory symptoms include nasal congestion, sneezing, rhinorrhea, hoarseness, stridor, dyspnea, bronchospasm and hypoxia.

In the cardiovascular system, anaphylaxis may manifest with dizziness, syncope, hypotension, arrhythmia, palpitations and substernal pain.

The gastrointestinal symptoms include nausea, vomiting, diarrhea, dysphagia and abdominal cramps. The other symptoms include headache, seizures, loss of consciousness, a feeling of anxiety and urinary urgency.

Workup

Anaphylaxis can be diagnosed on the basic of complete medical history including history about drugs and previous allergic reactions. The past medical history of seizure disorders, psychological issues, mastocytosis and food allergies may also help to confirm the diagnosis.

On general physical examination, the common signs include arrhythmia, pulmonary edema, hives, low blood pressure, mental confusion, rapid pulse, swelling of the eyes and face, wheezing and weakness.

Blood tests for histamine might be useful in diagnosing anaphylaxis due to insect stings or medications. However, they are not specific for the diagnosis.

Treatment

Anaphylaxis is a medical emergency that may require immediate therapy. There are different international recommendations for the management of anaphylaxis [9]. The general principles involved in the treatment include the following.

Cardiopulmonary resuscitation measures such as airway management, breathing and ventilation, supplemental oxygen, large volumes of intravenous fluids and close monitoring must be taken immediately [10].

The first line of approach to the treatment of anaphylaxis is the administration of adrenaline. It must be given intramuscularly into the mid anterolateral thigh as soon as the anaphylactic reaction is suspected. The injection may be repeated every 5-15 minutes.

Antihistamines and cortisone must be given to reduce inflammation of air passages and improve breathing. For circulatory collapse and hypotension, fluid therapy and vasopressors are given. It is very important to maintain airway by using bronchodilator drugs. Nebulized salbutamol may be effective for bronchospasm that does not resolve with epinephrine. A beta agonist such as albuterol is given to relieve breathing symptoms. Corticosteroids are administered in severe anaphylactic reactions. Oxygen inhalation is given for cyanosis or low oxygen tension PO2.

People prone to anaphylaxis are advised to have an ‘allergy action plan’. The action plan usually include use of epinephrine autoinjectors and counselling on avoidance of allergens. There are three types of autoinjectors including EpiPen, Jext and Emerade.

Immunotherapy is available for certain triggers now-a-days to prevent further episodes of anaphylactic reactions. A subcutaneous desensitization course has been found effective against stinging insects and for many foods.

Prognosis

In case of anaphylactic reactions, the prognosis is good if prompt treatment is available. The symptoms usually resolve with immediate, appropriate treatment. There are no long term effects of anaphylaxis other than the possibility of recurrence of the disease. Death usually occurs due to respiratory asphyxia or cardiovascular shock.

Etiology

Anaphylaxis can occur in response to any allergen [3]. Foods are the most common triggers in children and young adults. Many foods can trigger anaphylaxis such as ingestion of peanuts, wheat, nuts, milk, eggs, grapes, bananas and certain types of seafood such as shell fish [4].

Medications including certain antibiotics, vaccines, opiates, aspirin, non-steroidal anti-inflammatory drugs, local anesthetics, intravenous fluids and insulin can cause life threatening allergic reactions [5].

The stings of fire ants, bees, wasps, yellow jackets, hornets, kissing bugs can also trigger anaphylactic reactions in susceptible individuals [6].

Pollens and other inhaled allergens rarely cause anaphylaxis. The other risk factors include use of latex products such as gloves, blood products including plasma, immunoglobulins and beta-blockers such as epinephrine.

Epidemiology

Anaphylaxis is a severe allergic reaction that affects people of all ages. The number of people who gets anaphylaxis is 4 to 5 per 100,000 persons per year. The rates of anaphylactic reactions appear to be increasing being approximately 20 per 100,000 per year. In the United States, anaphylaxis leads to 500-1000 deaths per year. Food anaphylaxis is more common in children. Death from anaphylaxis is most commonly triggered by medications.

Sex distribution
Age distribution

Pathophysiology

Anaphylaxis is a severe allergic reaction that is triggered by foreign antigens [7]. The route of entry of the allergen is usually parenteral. Ingestion also is common. Inhalation is less common.

Anaphylaxis occurs within few minutes to hours after exposure to the antigen. Immunoglobulin E binds to the antigen and the systemic manifestations are caused by the release of inflammatory mediators such as histamine from mast cells and basophils. These mediators trigger vasodilation, increase the leakage of fluid from blood vessels, and cause heart muscle depression.

Non-immunological mechanisms involve substances that directly cause the degranulation of mast cells and basophils. These include agents such as contrast medium, opioids, hot and cold temperature and vibration.

Prevention

Anaphylaxis can be prevented by avoidance of known triggers such as foods and medications that have caused an allergic reaction in the past. The allergic reactions by stinging insects can be avoided by using insect repellents, wearing long sleeved shirts and pants and staying away from fields and grass.

A properly stocked emergency kit with prescribed medications available should be kept all the time. Wear a medical alert bracelet to indicate an allergy to specific drugs. The chances of exposure to food allergen can be reduced by checking the labels of foods before eating.

People who have a history of drug allergies may safely be given the offending medication after pretreatment with corticosteroids and antihistamines.

Summary

Anaphylaxis is a severe, life threatening systemic reaction caused by an IgE-mediated hypersensitivity reaction [1] [2]. It can be triggered by medications, foods, insect stings, exercise and unknown causes.

The condition is characterized by a sense of impending doom, tingling, flushing, shortness of breath, congestion, syncope, abdominal cramps and palpitations.

A severe allergic reaction usually occurs within 20 minutes to 2 hours of exposure to the triggering agents. The prognosis is good if the patient obtains medical treatment within 30 minutes.

Patient Information

Anaphylaxis is a serious allergic reaction. The most common allergic triggers are food, insect stings, medication and latex.

The symptoms of anaphylaxis skin rash, itching, shortness of breath, swelling of throat and low blood pressure. It may be life threatening if emergency treatment is not given.

Self-assessment

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References

  1. Simons FE. Anaphylaxis. The Journal of allergy and clinical immunology. Feb 2010;125(2 Suppl 2):S161-181.
  2. Johansson SG, Bieber T, Dahl R, et al. Revised nomenclature for allergy for global use: Report of the Nomenclature Review Committee of the World Allergy Organization, October 2003. The Journal of allergy and clinical immunology. May 2004;113(5):832-836.
  3. Kemp SF, Lockey RF. Anaphylaxis: a review of causes and mechanisms. The Journal of allergy and clinical immunology. Sep 2002;110(3):341-348.
  4. Wang J, Sampson HA. Food anaphylaxis. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology. May 2007;37(5):651-660.
  5. Suzuki I. [Anaphylaxis due to drugs]. Nihon rinsho. Japanese journal of clinical medicine. Oct 28 2007;65 Suppl 8:313-317.
  6. Bee-sting anaphylaxis. The Medical journal of Australia. Mar 6 1989;150(5):288.
  7. Simons FE. Anaphylaxis pathogenesis and treatment. Allergy. Jul 2011;66 Suppl 95:31-34.
  8. Lucke WC, Thomas H, Jr. Anaphylaxis: pathophysiology, clinical presentations and treatment. The Journal of emergency medicine. 1983;1(1):83-95.
  9. Alrasbi M, Sheikh A. Comparison of international guidelines for the emergency medical management of anaphylaxis. Allergy. Aug 2007;62(8):838-841.
  10. Willatts SM. Treatment of anaphylaxis. Anaesthesia. Oct 1979;34(9):910.

Media References

  1. Angioedema2010, CC BY-SA 3.0

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