Anaphylaxis is an uncommon, life-threatening condition that affects nearly the whole body. It is triggered by specific allergens, such as foods, insect stings, medications, or latex. Anaphylaxis can affect the skin, mucous membranes (inside the mouth), lungs, gastrointestinal tract, and heart.

While less severe allergic reactions can affect the skin, leading to itching and a rash, anaphylaxis may also involve tongue, lip, and airway swelling or a severe drop in blood pressure. It typically displays symptoms in two or more organ systems.

If you are having an allergic reaction and have trouble breathing or swelling around and inside your mouth and throat, call 911 immediately.  

This article will describe the signs and symptoms of anaphylaxis and will help you distinguish a severe allergic reaction from anaphylaxis. It will also go into treatments and prevention. 

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Anaphylaxis Symptoms

Differentiating a severe allergic reaction from anaphylaxis is challenging, and the disease processes are on a continuum. Allergic reactions may involve only one organ system, such as the skin breaking out in hives, but severe reactions can involve multiple organ systems.


Healthcare providers will diagnose anaphylaxis when you develop symptoms in multiple organs (skin plus mucous membranes, lungs, heart, or the gastrointestinal tract).

Symptoms of anaphylaxis include:

  • Itching
  • Hives
  • Flushing
  • Throat tingling or tightness
  • Lips swelling
  • Tongue and throat swelling
  • Nausea and vomiting
  • Diarrhea
  • Abdominal cramping
  • Wheezing
  • Shortness of breath
  • Trouble breathing
  • Palpitations
  • Dizziness
  • Low blood pressure
  • Cardiac arrest

Some People Don’t Develop Hives

While hives and itching are classically associated with allergic reactions and anaphylaxis and commonly occur in these cases, approximately 10% to 20% of people with anaphylaxis will not have a skin reaction beforehand.

Anaphylaxis can either occur all at once (be uniphasic) or a few hours later, after symptoms initially improve (be biphasic), which is more common in children than adults. Very rarely, anaphylaxis can last for days to weeks.

The most common type of anaphylaxis is uniphasic, and symptoms develop over approximately 30 to 60 minutes' time. However, fatal cases can occur within minutes of symptom onset, especially from insect venom and medication triggers.

Once treatment is initiated, the symptoms resolve within minutes to hours, and most of the time, they do not recur (70% to 90% of the time).

Anaphylactic Shock

Typically, healthcare professionals use the term "shock" to indicate that a person’s blood pressure is too low. Low blood pressure may be seen in severe anaphylaxis. But the presence of low blood pressure is not required for anaphylaxis to occur. As well, normal blood pressure measurements do not necessarily mean that anaphylaxis is not severe.

Anaphylaxis and anaphylactic shock are both severe illnesses, they can be fatal, and they require epinephrine for treatment. 

What Causes and Triggers Anaphylaxis?

Anyone can develop anaphylaxis, and the trigger doesn’t have to be something obvious or something a person was recently exposed to. Many triggers exist, but the most common triggers include: 

  • Foods (e.g., milk, eggs, wheat, soy, tree nuts, peanuts, shellfish, fin fish)
  • Venom (e.g., bees, fire ants)
  • Medications (e.g., penicillin, cephalosporins, sulfonamides, aspirin, nonsteroidal anti-inflammatory drugs, or NSAIDs)
  • Latex
  • Unknown triggers

Anaphylaxis at Home vs. in the Hospital

Most fatal cases of medication-induced anaphylaxis happen in a hospital setting. Most fatal cases of anaphylaxis in the outpatient setting are due to food.

Risk factors for severe anaphylaxis include the following:

  • Being older than 65
  • Having a history of mastocytosis (a rare condition in which immune cells called mast cells build up in the body)
  • Taking certain medications
  • Experiencing other health problems, such as heart disease and lung disease
  • Having a food allergy


There is a higher incidence of anaphylaxis in northern than southern latitudes.

How Do You Treat Anaphylaxis?

Once a person has developed anaphylaxis, treatment with epinephrine is necessary. If an epinephrine auto-injector (EpiPen) is available, it should be used. You must then get to an emergency room for further care and monitoring. If no EpiPen is available, call 911 or get immediate transport to an emergency room.

Healthcare providers can give other medications at the same time as epinephrine, but getting epinephrine is paramount. Those who have developed wheezing are also treated with bronchodilators like albuterol.

Use of an EpiPen

An EpiPen auto-injector does most of the work for you. To use an EpiPen, follow these steps:

  1. Remove the pen from the carrier case.
  2. Place the orange part against your upper outer thigh.
  3. Remove the blue safety release.
  4. Press the injector button.

After using an EpiPen, always call 911 and get emergency medical help. You need monitoring and assessment for further treatment.

Anaphylaxis Emergency Treatment

The emergency department treatment of anaphylaxis is an all-out effort and includes epinephrine in all cases. Often, allergic reactions are treated stepwise depending on the severity of the disease, but epinephrine must be given immediately, even while awaiting all other treatments.

The list of treatments includes:

  • Antihistamines
  • Albuterol nebulizer if wheezing is present
  • Intravenous fluid for low blood pressure
  • Epinephrine auto-injector or intravenous epinephrine in the emergency department
  • Oxygen, as needed
  • Intubation for airway control
  • Cardiopulmonary resuscitation (CPR) for cardiac arrest

How to Prevent Future Anaphylaxis

The primary and most obvious way to prevent anaphylaxis is by avoiding triggers. For instance, if you've had a severe allergic reaction in the past to a bee sting, try to avoid bees. If you have a nut allergy, know what ingredients are in your cookies and other foods before eating them. 

While prevention is vital, having the best treatments on hand can prevent severe symptoms and death. If you or someone in your home has suffered a severe allergic reaction at any time, keep an EpiPen kit on hand at all times.

It’s excellent practice for all healthcare providers to prescribe a two-pack EpiPen to all people treated for allergic reactions in an emergency department or clinic. Make sure you have this prescription and keep it updated every few years. 

Even Expired EpiPens Can Work

Most pharmacists indicate the EpiPen lasts 12 to 18 months, but even EpiPens that are five to seven years old still contain around 70% to 80% of active medicine. Some epinephrine is better than no epinephrine, so use it if that’s all you have.


Anaphylaxis is a life-threatening emergency, but it is uncommon. Less than 2% of the population will develop anaphylaxis sometime during their life.

In the United States, hospital visits for anaphylaxis are increasing. Still, it’s unclear whether this is because of more allergic symptoms, more education surrounding the disease, or earlier awareness by healthcare providers in treating the disease early with epinephrine.

Whatever the case, fatal anaphylaxis is rare. However, everyone with a previous allergic reaction or known risk factors for severe anaphylaxis (asthma, lung disease, older age) should keep EpiPens on hand. They can save a life.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Christine Zink, MD

Dr. Christine Zink, MD, is a board-certified emergency medicine with expertise in the wilderness and global medicine. She completed her medical training at Weill Cornell Medical College and residency in emergency medicine at New York-Presbyterian Hospital. She utilizes 15-years of clinical experience in her medical writing.

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