Anaphylaxis is a severe, potentially life-threatening allergic reaction. It can occur within seconds or minutes of exposure to something you're allergic to, such as peanuts or bee stings.
Anaphylaxis causes the immune system to release a flood of chemicals that can cause you to go into shock — blood pressure drops suddenly and the airways narrow, blocking breathing. Signs and symptoms include a rapid, weak pulse; a skin rash; and nausea and vomiting. Common triggers include certain foods, some medications, insect venom and latex.
Anaphylaxis requires an injection of epinephrine and a follow-up trip to an emergency room. If you don't have epinephrine, you need to go to an emergency room immediately. If anaphylaxis isn't treated right away, it can be fatal.
Products & Services
Anaphylaxis symptoms usually occur within minutes of exposure to an allergen. Sometimes, however, anaphylaxis can occur a half-hour or longer after exposure. In rare cases, anaphylaxis may be delayed for hours. Signs and symptoms include:
- Skin reactions, including hives and itching and flushed or pale skin
- Low blood pressure (hypotension)
- Constriction of the airways and a swollen tongue or throat, which can cause wheezing and trouble breathing
- A weak and rapid pulse
- Nausea, vomiting or diarrhea
- Dizziness or fainting
When to see a doctor
Seek emergency medical help if you, your child or someone else you're with has a severe allergic reaction. Don't wait to see if the symptoms go away.
If you have an attack and you carry an epinephrine autoinjector, administer it right away. Even if symptoms improve after the injection, you still need to go to an emergency room to make sure symptoms don't recur, even without more exposure to the allergen. This second reaction is called biphasic anaphylaxis.
Make an appointment to see your provider if you or your child has had a severe allergy attack or signs and symptoms of anaphylaxis in the past.
The diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor who specializes in allergies and immunology.
From Mayo Clinic to your inbox
Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.
ErrorEmail field is required
ErrorInclude a valid email address
To provide you with the most relevant and helpful information, and understand which
information is beneficial, we may combine your email and website usage information with
other information we have about you. If you are a Mayo Clinic patient, this could
include protected health information. If we combine this information with your protected
health information, we will treat all of that information as protected health
information and will only use or disclose that information as set forth in our notice of
privacy practices. You may opt-out of email communications at any time by clicking on
the unsubscribe link in the e-mail.
Thank you for subscribing!
You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.
Sorry something went wrong with your subscription
Please, try again in a couple of minutes
The immune system produces antibodies that defend against foreign substances. This is good when a foreign substance is harmful, such as certain bacteria or viruses. But some people's immune systems overreact to substances that don't normally cause an allergic reaction.
Allergy symptoms aren't usually life-threatening, but a severe allergic reaction can lead to anaphylaxis. Even if you or your child has had only a mild anaphylactic reaction in the past, there's a risk of more severe anaphylaxis after another exposure to the allergy-causing substance.
The most common anaphylaxis triggers in children are food allergies, such as to peanuts and tree nuts, fish, shellfish, wheat, soy, sesame and milk. Besides allergy to peanuts, nuts, fish, sesame and shellfish, anaphylaxis triggers in adults include:
- Certain medications, including antibiotics, aspirin and other pain relievers available without a prescription, and the intravenous (IV) contrast used in some imaging tests
- Stings from bees, yellow jackets, wasps, hornets and fire ants
Although not common, some people develop anaphylaxis from aerobic exercise, such as jogging, or even less intense physical activity, such as walking. Eating certain foods before exercise or exercising when the weather is hot, cold or humid also have been linked to anaphylaxis in some people. Talk with your health care provider about precautions to take when exercising.
If you don't know what triggers an allergy attack, certain tests can help identify the allergen. In some cases, the cause of anaphylaxis is not identified (idiopathic anaphylaxis).
There aren't many known risk factors for anaphylaxis, but some things that might increase the risk include:
- Previous anaphylaxis. If you've had anaphylaxis once, your risk of having this serious reaction increases. Future reactions might be more severe than the first reaction.
- Allergies or asthma. People who have either condition are at increased risk of having anaphylaxis.
- Certain other conditions. These include heart disease and an irregular accumulation of a certain type of white blood cell (mastocytosis).
An anaphylactic reaction can be life-threatening — it can stop your breathing or your heartbeat.
The best way to prevent anaphylaxis is to stay away from substances that cause this severe reaction. Also:
- Wear a medical alert necklace or bracelet to indicate you have an allergy to specific drugs or other substances.
- Keep an emergency kit with prescribed medications available at all times. Your provider can advise you on the contents. If you have an epinephrine autoinjector, check the expiration date and be sure to refill the prescription before it expires.
- Be sure to alert all your providers to medication reactions you've had.
- If you're allergic to stinging insects, use caution around them. Wear long-sleeved shirts and pants; don't walk barefoot on grass; don't wear bright colors; don't wear perfumes, colognes or scented lotions; and don't drink from open soda cans outdoors. Stay calm when near a stinging insect. Move away slowly and don't slap at the insect.
If you have food allergies, carefully read the labels of all the foods you buy and eat. Manufacturing processes can change, so it's important to periodically recheck the labels of foods you commonly eat.
When eating out, ask how each dish is prepared, and find out what ingredients it contains. Even small amounts of food you're allergic to can cause a serious reaction.
Even if you're careful, at some point you'll likely be exposed to what you're allergic to. Fortunately, you can respond quickly and effectively to an allergy emergency by knowing the signs and symptoms of an anaphylactic reaction and having a plan to quickly treat those symptoms.
Oct. 02, 2021