Skip to main content
Read about

Anaphylaxis: What It Is, Treatment Options, & Setting an Action Plan

Tooltip Icon.
Last updated June 4, 2024

Anaphylaxis quiz

Take a quiz to find out what's causing your anaphylaxis.

Anaphylaxis is a severe allergic reaction that occurs within seconds to minutes of exposure to an allergen and can result in rashes, nausea, difficulty breathing and shock.

Anaphylaxis quiz

Take a quiz to find out what's causing your anaphylaxis.

Take anaphylaxis quiz

What is anaphylaxis?


Anaphylaxis is a life-threatening condition most commonly caused by an allergic reaction. In anaphylaxis, two types of immune cells — mast cells and basophils — are suddenly activated and release numerous inflammatory substances that cause blood vessels to dilate and become leaky, which can lead to low blood pressure, swelling, and damage to organs.

Symptoms of anaphylaxis include itching, redness, and warmth in the form of hives, as well as itching or swelling of the lips, tongue, mouth, or around the eyes, as well as difficulty breathing and nasal congestion. Several other symptoms are also likely.

Anaphylaxis is a medical emergency. Treatment options will likely involve an epinephrine injection (same contents as in an EpiPen), followed by oxygen and IV fluids, other medications, and an action plan for possible future incidents.

Recommended care

Call 911 immediately for an ambulance. If you have been prescribed an epinephrine pen, use it. Don't do this if you have never been prescribed one!

Hallmarks of anaphylaxis

Symptoms of anaphylaxis usually develop within seconds to minutes after exposure to a trigger, although in some cases symptoms develop hours later. Symptoms may be mild and resolve on their own, but in many cases, the symptoms can worsen rapidly and even lead to death if not treated as an emergency. In some cases, the symptoms may recur within 12 hours of the initial episode, known as a biphasic reaction.

Main symptoms

The main symptoms experienced by most people with anaphylaxis include:

  • Itching, redness, warmth, and/or hives: Hives, which are raised itchy red bumps on the skin, usually occur all over the body shortly after exposure to the trigger.
  • Itching, tingling, and/or swelling of the lips, tongue, or mouth: In severe cases, the swelling may make it difficult to swallow or breathe.
  • Itching or swelling around the eyes and/or red eyes: The eyes may also tear from the irritation.
  • Difficulty breathing or noisy breathing: There may be a sensation of choking or the throat closing. The noisy breathing can be heard either when breathing in or breathing out.
  • Nasal congestion or discharge: This may occur rapidly in some people with anaphylaxis.

Other symptoms

Other symptoms that may occur in some people with anaphylaxis include:

  • Abdominal pain, cramps, nausea, vomiting, and/or diarrhea: This occurs in about half of people with anaphylaxis. These symptoms are caused by swelling of the gastrointestinal tract.
  • Dizziness, lightheadedness, confusion, or passing out: During anaphylaxis, the blood vessels throughout the body dilate, causing a fall in blood pressure and the prevention of enough blood from reaching the brain, which leads to these symptoms.
  • Chest pain or feeling the heart racing: These symptoms may occur because, during anaphylaxis, the heart beats faster to try to compensate for the low blood pressure.
  • Anxiety and/or a sense of impending doom

Anaphylaxis causes

Most cases of anaphylaxis are caused by a reaction to an allergen, such as foods, insect stings, and bites, or certain medications. Some cases of anaphylaxis are caused by a non-allergic type reaction, in which mast cells and basophils are directly activated. Other common causes of anaphylaxis can also be related to exposures listed below.

1. Foods

Foods are the most common cause of anaphylaxis in children, teenagers, and young adults. Common foods that can trigger anaphylaxis include:

  • Peanuts
  • Tree nuts
  • Crustacean shellfish
  • Milk
  • Eggs

2. Insect stings and bites

Insect stings and bites are a common cause of anaphylaxis, especially among older adults. Common insects that can trigger anaphylaxis include:

  • Bees
  • Wasps
  • Yellowjackets
  • Hornets
  • Fire ants

3. Medications

Medications are another common cause of anaphylaxis, especially among older adults. Common medications that can trigger anaphylaxis include:

  • Antibiotics
  • Aspirin
  • Some over-the-counter pain medications
  • Intravenous contrast used in some imaging studies

In addition, some medications can exacerbate anaphylactic reactions or prevent the body from responding to anaphylaxis. These include:

  • Alcohol
  • Opioids
  • Certain medications used for heart disease and high blood pressure

Other exposures

Being exposed to the following can also cause anaphylaxis or an allergic reaction in some people:

  • Latex: Many medical centers now use latex-free gloves to reduce the risk of triggering an allergic reaction.
  • Exercise: This is a special type of anaphylaxis known as exercise-induced anaphylaxis.
  • Exposure to cold or heat

Treatment options and prevention for anaphylaxis

The most important initial treatment for anaphylaxis involves administering epinephrine. Other specific components of treatment include oxygen and IV fluids, other medications, as well as education to better handle any future incidents.

Epinephrine injection

Epinephrine is injected into a vein (IV) or a muscle by a clinician to restore blood pressure and heart function during anaphylaxis.

  • Details: The best way to give epinephrine is to inject it into a muscle, usually the side of the thigh.
  • Types: People who have had episodes of anaphylaxis may be prescribed an epinephrine autoinjector, such as EpiPen, Adrenaclick, or Auvi-Q, and they will be instructed how to use it. In some cases, additional epinephrine may be given intravenously after it has been injected into the muscle.

Oxygen and IV fluids

In addition to an epinephrine injection, you may also be given:

  • Supplemental oxygen: This may be given through a mask to ensure there is adequate oxygen in the blood. If swelling in the mouth or throat is causing difficulty breathing, intubation may be necessary.
  • Intravenous fluids: IV fluids are given to maintain blood pressure. Because anaphylaxis causes the blood vessels throughout the body to dilate, a large amount of IV fluid may be needed to maintain a normal blood pressure.

Other medications

To help relieve symptoms after epinephrine has been given, the following may also be used.

  • Albuterol: This may be used to help with wheezing and difficulty breathing.
  • Diphenhydramine (Benadryl) or other antihistamines: Certain medications may be given to relieve itching.
  • Steroids: Such as methylprednisolone, which may be given to help reduce inflammation.

Education and future action plan

Education and the creation of an anaphylaxis emergency action plan is important after the acute episode of anaphylaxis has been treated to avoid and manage future anaphylaxis episodes. This may involve:

  • Creating a list of possible causes to avoid
  • A prescription of and instructions for how to use epinephrine autoinjectors
  • What to do if symptoms of anaphylaxis recur

When to seek further consultation for anaphylaxis

If you experience any symptoms of anaphylaxis, such as hives, swelling, or trouble breathing, you should go to the emergency room or call an ambulance immediately.

If you believe you are having another episode and you have an autoinjector

You should use your autoinjector if you feel confident doing so and you feel symptoms of another episode of anaphylaxis coming on. You should go to the emergency room immediately after.

Questions your doctor may ask to determine anaphylaxis

  • Are you sick enough to consider going to the emergency room right now?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Any fever today or during the last week?
  • Have you experienced any nausea?
  • Have you lost your appetite recently?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Share your story
Once your story receives approval from our editors, it will exist on Buoy as a helpful resource for others who may experience something similar.
The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
Read full bio

Was this article helpful?

Tooltip Icon.
Read this next
Slide 1 of 6


  1. Anaphylaxis symptoms and causes. Mayo Clinic. Published January 5, 2018. Mayo Clinic Link.
  2. Anaphylaxis. American College of Allergy, Asthma, & Immunology. Updated January 29, 2018. ACAAI Link
  3. Anaphylaxis: A severe allergic reaction. Asthma and Allergy Foundation of America. Updated February 2017. AAFA Link
  4. Tupper J, Visser S. Anaphylaxis: A review and update. Canadian Family Physician. 2010;56(10):1009-1011. NCBI Link
  5. Anaphylaxis. U.S. National Library of Medicine: MedlinePlus. Updated December 6, 2018. MedlinePlus Link