Anaphylaxis

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What is anaphylaxis?

Anaphylaxis, also referred to as an anaphylactic reaction or anaphylactic shock, is a severe and sometimes life-threatening allergic reaction. While it is not common, the severity of the reaction and its rapid onset, usually within a few minutes of exposure to the allergen, require immediate medical care.

Anaphylaxis is caused by your body’s severe immune reaction to an allergen, leading to the release of chemicals that cause swelling and other severe symptoms. These symptoms can lead to swelling of the tissues around the throat and face that are severe enough to cause breathing difficulty and a sudden drop in blood pressure.

Almost any allergen can cause anaphylaxis, and allergens that lead to anaphylaxis vary from person to person. These allergens can include foods, such as nuts or shellfish, insect or spider stings or bites, or medications, such as aspirin or penicillin.

Once your anaphylactic reaction has been treated, health care professionals can help to identify the allergen that caused your reaction by using a series of tests, such as skin exposure to small amounts of different allergens, or by reviewing dietary logs with you. Once the triggering allergen is identified, you can best prevent anaphylaxis by avoiding the allergen and carrying a portable epinephrine injection kit, if recommended, to treat any serious allergic reactions.

Anaphylaxis is a severe and life-threatening condition. Seek immediate medical care (call 911) if you experience any of the symptoms of anaphylaxis, such as sudden swelling of the face, throat or lips; difficulty breathing; dizziness; hives or skin changes; and a fast heartbeat.

What are the symptoms of anaphylaxis?

Symptoms of anaphylaxis may include severe swelling and a drop in blood pressure. These symptoms will typically occur within several minutes of exposure to the triggering allergen, although they may take up to a few hours to appear. Skin findings (itching, hives, rash, etc.) occur in nearly 90% of anaphylactic episodes.

Serious symptoms that might indicate a life-threatening condition

In almost all cases, anaphylaxis is a severe and possibly life-threatening condition. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms:


What causes anaphylaxis?

Anaphylaxis is caused when your body detects allergens you may be sensitized to, and then triggers an immune response to those allergens. This immune response prompts the release of chemicals, specifically histamine, that cause swelling of tissues in the area of the allergen, as well as a decrease in blood pressure, among other symptoms.

Anaphylaxis is caused by allergies to a variety of allergens, including but not limited to:

  • Bites or stings, including those from ants, bees, spiders or wasps
  • Contrast materials used for X-ray or other imaging studies
  • Exercise (not common)
  • Foods, including dairy products, fruit, nuts, shellfish, or soy
  • Latex
  • Medications or vaccines including allergy shots, anesthetics, aspirin, or penicillin
  • Preservatives

What are the risk factors for anaphylaxis?

Few risk factors are associated with an increased likelihood of developing anaphylaxis. Not all people with risk factors will experience anaphylactic reactions. Risk factors for anaphylaxis include:

  • Asthma or allergies
  • Personal or family history of anaphylaxis

Reducing your risk of anaphylaxis

While there are not any measures you can take to directly avoid developing anaphylaxis, you can reduce your risk of exposure to allergens that trigger anaphylactic reactions. Additionally, you can take steps to decrease treatment time if you develop an anaphylactic reaction. These steps include:

  • Avoiding allergens that trigger anaphylaxis
  • Reading labels on food products
  • Wearing a medical ID tag

How is anaphylaxis treated?

Anaphylaxis is a medical emergency and should be treated immediately (call 911). While waiting for medical professionals to arrive, lie down and elevate your feet. If you have an emergency anaphylaxis kit, inject yourself with epinephrine.

Immediate treatments for anaphylaxis

Once you are in the care of medical professionals, the treatment used will depend on the severity of your reaction. Treatment options used by medical professionals may include:

  • Administration of epinephrine, also known as adrenaline, or other drugs, such as antihistamines or corticosteroids, via injection or intravenously (IV)

  • Other medications, such as steroids or antihistamines and inhaled medications to support respiratory function

  • Oxygen supplementation

Long-term treatment for anaphylaxis

Depending on the allergen that triggers your anaphylaxis, long-term treatment may help to reduce your chances of recurring anaphylactic reactions. Long-term treatment options include:

  • Getting allergy shots if your anaphylaxis is caused by certain allergens such as insect bites

  • Going through desensitization therapy, which involves taking increasing doses of medication, if your anaphylaxis is caused by medications

  • Obtaining and always having with you an emergency anaphylaxis kit containing epinephrine if prescribed by your doctor

  • Wear a medical alert bracelet or carry similar information in your wallet

What are the potential complications of anaphylaxis?

Anaphylaxis can be a life-threatening condition and should always be treated as an emergency situation. Complications of untreated anaphylaxis can be serious or life-threatening. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of anaphylaxis include:

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Sep 6
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Anaphylaxis. PubMed Health, a service of the NLM from the NIH. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001847/
  2. Allergic reactions. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000005.htm
  3. Simons FE, Ardusso LR, Bilò MB, et al. World Allergy Organization anaphylaxis guidelines: summary. J Allergy Clin Immunol 2011; 127:587.