Anaphylaxis is a severe and potentially life-threatening allergic reaction.¹ Like other allergy symptoms, it’s triggered when the immune system overreacts and releases histamine (among other chemicals) in response to an allergen, such as peanuts, shellfish, latex, insect venom, dust mites, and countless more.²

Often, histamine causes symptoms such a runny nose, itchy/watery eyes, etc.³ But sometimes, the body releases a flood of chemicals that can send the body into anaphylactic shock.¹ Blood pressure may drop suddenly, and airway tissues may swell, causing wheezing, shortness of breath, and loss of consciousness among other symptoms. If not treated immediately, anaphylaxis may lead to death.³

While anaphylaxis is rare, it’s an extremely serious condition, and dealing with it can be scary. But studying the causes, signs, and symptoms of anaphylaxis and learning about potential risk factors and management strategies may help lessen anxiety and prepare you and others to deal with anaphylaxis if it occurs. So here’s a primer to help you do just that.

What are the signs and symptoms of anaphylaxis?

Each anaphylactic experience is unique. However, there are several common symptoms, most of which occur within five to 30 minutes of contacting the allergen. However, in some cases, symptoms can start more than an hour later.³

While some people show life-threatening reactions almost immediately, others may experience early signs of anaphylaxis. Particularly for anyone with a history or high risk of anaphylaxis, it’s important to recognize early symptoms (if present) and immediately seek treatment.⁴

Initial Signs of Anaphylaxis

When exhibited, early signs of anaphylaxis may include:^3-5

• Itchy mouth, throat, eyes, and/or face
• Patchy red skin, hives, welts
• Itchy scalp, palms, and/or soles of feet, possibly extending to the ear canal, lips, and/or genitals
• Nasal congestion
• Throat tightness, hoarseness, and/or changes in the tone of voice
• Swelling of lips and/or tongue

For some people, the first signs of anaphylaxis are far more severe and usually involve more than one part of the body, such as the skin, mouth, lungs, heart, and/or gut.⁶

Severe Anaphylaxis Symptoms

Along with the initial signs of anaphylaxis, additional symptoms may include:^3,5,6

• Shortness of breath, trouble breathing, coughing and/or wheezing (i.e., a whistling sound while breathing)
• Dizziness and/or fainting
• Stomach cramping, pain, bloating, vomiting, and/or diarrhea
• Uterine cramps
• Feelings of dread or impending doom
• Chest tightness
• Trouble swallowing
• Increased heart rate and/or low blood pressure
• Weak pulse
• Confusion
• Sudden weakness
• Dizziness/fainting
• Loss of consciousness

According to the Cleveland Clinic (a nonprofit academic medical center), approximately 20 percent of people with anaphylaxis experience biphasic anaphylaxis. With this type of reaction, people experience some of the aforementioned symptoms, which then go away. However, hours or sometimes even days after this first wave of symptoms, they experience a second round of severe symptoms.³

Given the risks of biphasic reactions, it’s important to monitor people who have experienced anaphylaxis for hours or perhaps even days after they’ve seemingly recovered.  

What causes anaphylaxis?

While there may be other causes of anaphylaxis, such as exercise, allergens are the main culprits. Among them, food allergens are the most frequent triggers of anaphylaxis in children, and insect venom and various drug allergies are the most prevalent offenders in adults.⁷ Additionally, according to an article published in The Journal of Allergy and Clinical Immunology, drugs are the most common reported cause of fatal anaphylaxis in countries such as Australia, New Zealand, the United Kingdom, Brazil, and the United States.⁸

Here are some of the most common allergies that can cause anaphylaxis, along with some links to help you learn more about each one. 

What are some anaphylaxis risk factors?

While anaphylaxis is somewhat unpredictable, several factors may increase the risk of anaphylaxis. 

• Previous anaphylaxis. The risk of anaphylaxis is elevated for those that have already experienced it; plus, subsequent reactions may be more severe.¹
• Cardiovascular disease. According to one study, 71 percent of fatal drug anaphylaxis occurred in people with cardiovascular disease.⁸
• Mastocytosis. While rare, mastocytosis is caused by an excess amount of mast cells in body tissues.¹⁸ While it leads to a host of symptoms depending on condition type, people with systemic mastocytosis have an increased risk of anaphylaxis.¹⁶
• Asthma. Asthma affects 70 to 75 percent of those suffering fatal food anaphylaxis in the United Kingdom and Australia, according to a recent study.⁸
• Exercise. Exercise-induced anaphylaxis typically occurs after vigorous physical activity.⁶ Symptoms may initially include fatigue, flushing, and skin conditions such as hives, welts, and/or a rash.¹⁶ Additional risk factors that may affect exercise-induced anaphylaxis include the use of drugs or alcohol, temperature and seasonal changes, and consumption of foods prior to exercise.⁶ The most common foods that may be related to this condition in adults include celery, shellfish, cheese, tomatoes, and alcohol.⁴
• Other factors. Stress, acute infections, and perimenstrual status may also increase the risk for anaphylaxis.⁸

What can you do to prevent and treat anaphylaxis?

To reduce the risk of anaphylaxis, it’s critical for those with allergies to first understand which allergens they’re sensitized to and to then take steps to reduce exposure. One of the best ways to identify your possible triggers is a simple blood test.

Paired with your symptom history and physical exam, a specific IgE blood test for allergies can help your healthcare provider determine exactly which allergens may cause allergic reactions. Additionally, a specific IgE allergen component test (along with other factors) may help your provider better predict your risk of a serious reaction such as anaphylaxis.   

To prepare for a healthcare visit, complete our symptom tracker, which will generate a comprehensive symptom profile you can then review with your healthcare provider to decide if a specific IgE blood test is right for you.

Once you’ve identified your triggers, there are several steps you can take to prepare for and/or prevent a reaction and to deal with emergencies.

For more articles like this, check out our Living with Allergies section of our website and our Allergen Fact Sheets, which provide basic info and exposure-reduction tips for more than 60 allergens, including mold, pet dander, cockroaches, dust mites, pollen, alpha-Gal, insect venom, and more).