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ANAPHYLAXIS OVERVIEW — Anaphylaxis is a potentially deadly allergic reaction that is rapid in onset. It is most often caused or triggered by foods, medications, and insect stings. There are many other possible triggers.
Anaphylactic reactions are unpredictable. Many people who experience it have a known allergy. Some have had one or more milder allergic reactions previously. Others, who are not even aware that they have an allergy, can suddenly experience severe anaphylaxis. Even the first episode of anaphylaxis can be fatal.
The severity of anaphylactic reactions can be minimized by recognizing the symptoms early, having proper medication available for self-treatment, and seeking emergency medical care promptly. This topic reviews anaphylaxis treatment and prevention. Separate topics discuss the symptoms and diagnosis of anaphylaxis and how to use an epinephrine autoinjector. (See "Patient education: Anaphylaxis symptoms and diagnosis (Beyond the Basics)" and "Patient education: Using an epinephrine autoinjector (Beyond the Basics)".)
ANAPHYLAXIS TREATMENT — A person who has had an anaphylactic reaction should talk with his/her health care professional and develop an anaphylaxis emergency action plan for responding to future reactions. (See "Anaphylaxis: Emergency treatment".)
Many people find that having an anaphylaxis treatment plan is reassuring, even if it is never needed. A critical component of the plan is having an epinephrine autoinjector available at all times and knowing when and how to use it. (See 'Self-treatment with epinephrine' below.)
Get emergency help — Because anaphylaxis can be life-threatening, it should be treated as a medical emergency. If you are experiencing a sudden allergic reaction that might be anaphylaxis, use your epinephrine autoinjector, and then call 911 or emergency medical services (or have someone else call for you). If you are home alone, make sure that the door is unlocked so that the emergency team can enter.
Self-treatment with epinephrine — If you have a history of anaphylaxis, you should carry at least one epinephrine autoinjector with you at all times. A full description of epinephrine autoinjectors is available separately. (See "Patient education: Using an epinephrine autoinjector (Beyond the Basics)".)
Epinephrine is the only medicine that optimally treats anaphylactic reactions. It is most effective when it is given promptly, before symptoms become severe. Neither antihistamines, which mainly relieve hives and itching, nor asthma inhalers (puffers), which mainly relieve coughing and wheezing, can fully treat anaphylaxis effectively. These medications should not be substituted for epinephrine.
Remove the cause — The trigger for the anaphylactic reaction should be promptly removed, whenever possible. For example, if you have been stung by a bee and the stinger is still in the skin, flick it out immediately.
Go to the hospital — After injecting epinephrine, it is important to be evaluated in a hospital emergency department where doctors and nurses can monitor you and if necessary, give oxygen, insert a breathing tube and/or IV. When needed, extra doses of epinephrine, intravenous fluids, and other medications can also be given.
There is an additional reason to go to the emergency department. Up to 20 percent of people with anaphylaxis have biphasic (two-phase) anaphylaxis, in which symptoms resolve and then recur without further exposure to the trigger. There is no good way to predict whether a biphasic reaction will occur. Because of this, many allergy specialists advise patients to go to the emergency department to be monitored so they can receive additional treatment if the symptoms do recur.
ANAPHYLAXIS PREVENTION — Anaphylaxis is a frightening experience. If you have had one anaphylactic reaction, you are at increased risk for another. It is normal to be anxious about this. The following steps can help to reduce the risk of a future anaphylactic reaction:
See an allergist — Anyone who has experienced an anaphylactic reaction should be evaluated by a doctor with specific training and experience in the diagnosis and treatment of anaphylaxis who can help you to prevent recurrences. Board-certified allergists have such training and experience. (See "Anaphylaxis: Confirming the diagnosis and determining the cause(s)".)
Testing to determine the cause or trigger — It is important to confirm the trigger(s) of the anaphylactic reaction. Allergists can perform and interpret skin or blood tests to confirm your specific anaphylaxis trigger(s).
For the most reliable results, skin tests should be performed at least four weeks after an anaphylactic reaction because if done too soon after the event, such tests may give negative results when the person truly does have an allergy. Antihistamines and certain other medications need to be stopped for at least four days before skin tests are performed.
In some cases, allergy tests do not identify any specific trigger. This condition is called idiopathic anaphylaxis. Some people have too many mast cells or overly active mast cells. It is more common in adults than in children. An allergist can provide the best advice about how to assess this condition (other laboratory tests may be needed) and how to manage it.
Avoiding triggers — When a trigger has been identified, you should avoid it. However, avoiding some triggers, such as common foods, can be difficult.
Foods — If you have experienced an anaphylactic reaction due to a food, you should eliminate that food from your diet. This requires that you read and understand food labels and ask about the preparation and content of all foods, especially when eating away from home. This recommendation applies to snacks as well as meals and to everything that you plan to ingest, not just the foods that are most likely to contain the trigger. More information about food allergy treatment and prevention is available separately. (See "Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)" and "Patient education: Food allergen avoidance (Beyond the Basics)".)
An allergist can provide strategies for identifying allergens in processed/packaged foods and when dining out. In addition, practical information is available online from Food Allergy Research & Education (www.foodallergy.org/).
Insect stings — People with an allergy to a stinging insect (bees, yellow jackets, wasps, hornets, or fire ants) should avoid locations where these insects are seen and, if allergic to yellow jackets, should avoid drinking from open beverage containers outdoors. (See "Stinging insects: Avoidance" and "Patient education: Imported fire ants (Beyond the Basics)".)
A course of allergy shots is recommended for anyone who has had an anaphylactic reaction after an insect sting. The injections are typically given for five years. They dramatically reduce the person's risk of another episode of anaphylaxis. (See "Hymenoptera venom immunotherapy: Efficacy, indications, and mechanism of action".)
Medications — If you have an allergy to a medication, you should learn and record all the different names of that medication and the settings in which you are likely to encounter it. Ask your health care providers to note your allergy in your medical record and consider a medical identification device.
Wear medical identification — People who have experienced an anaphylactic reaction should consider wearing a medical identification bracelet or similar medical identification tag. If another reaction occurs and you are too ill to explain your condition, the words "anaphylaxis" or "anaphylactic reaction" will help emergency responders provide prompt and proper care.
The tag should include a list of your known allergies as well as the names and phone numbers of your emergency contacts. Some devices provide a toll-free number that emergency medical workers can call to find out a person's medical history, list of medications, emergency contact numbers, and health care provider names and numbers.
WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient education: Anaphylaxis (The Basics)
Patient education: Food allergy (The Basics)
Patient education: Epinephrine autoinjectors (The Basics)
Patient education: Angioedema (The Basics)
Patient education: Insect allergy (The Basics)
Patient education: Peanut allergy (The Basics)
Patient education: Drug allergy (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient education: Anaphylaxis symptoms and diagnosis (Beyond the Basics)
Patient education: Using an epinephrine autoinjector (Beyond the Basics)
Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)
Patient education: Food allergen avoidance (Beyond the Basics)
Patient education: Imported fire ants (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Anaphylaxis: Emergency treatment
Bee, yellow jacket, wasp, and other Hymenoptera stings: Reaction types and acute management
Clinical manifestations of food allergy: An overview
Diagnosis of Hymenoptera venom allergy
Diagnostic evaluation of IgE-mediated food allergy
Differential diagnosis of anaphylaxis in adults and children
Drug eruptions
Fatal anaphylaxis
Food-induced anaphylaxis
History and physical examination in the patient with possible food allergy
Diagnosis and treatment of an acute reaction to a radiologic contrast agent
Laboratory tests to support the clinical diagnosis of anaphylaxis
Pathophysiology of anaphylaxis
Anaphylaxis: Confirming the diagnosis and determining the cause(s)
Stinging insects: Avoidance
Hymenoptera venom immunotherapy: Efficacy, indications, and mechanism of action
The following organizations also provide reliable health information.
●American Academy of Allergy, Asthma & Immunology (https://acaai.org/allergies/anaphylaxis)
●Food Allergy Research & Education (www.foodallergy.org)
●American College of Allergy, Asthma & Immunology (acaai.org)
●Food Allergy Canada (foodallergycanada.ca)
●Anaphylaxis Campaign (www.anaphylaxis.org.uk)
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