What Is Anaphylaxis?

Anaphylaxis is a severe and potentially life-threatening allergic reaction that occurs rapidly in four stages after exposure to an allergen. This reaction occurs due to an overreactive immune response to the allergen, which the body mistakenly perceives as harmful. These can be foods, medications, insect stings, latex, or something else.

The immune system releases a flood of chemicals that can cause a range of body-wide symptoms. Symptoms include difficulty breathing, swelling of the face and throat, rapid heartbeat, low blood pressure, gastrointestinal (GI) distress, and skin reactions like hives or itching.

Anaphylaxis is a medical emergency that requires immediate epinephrine (adrenaline) treatment. Epinephrine counteracts the allergic reaction and stabilizes symptoms. Some people may require additional treatments. If left untreated, anaphylaxis can progress rapidly, leading to complications or death.

About one in 50 Americans have experienced anaphylaxis. Understanding anaphylaxis is crucial for people at risk and their families to recognize the signs and symptoms. Appropriate management can save lives.  

Anaphylaxis Symptoms 

Anaphylaxis symptoms develop suddenly and quickly progress. Specific symptoms vary from person to person, but anaphylaxis can affect the entire body.

Respiratory Symptoms

Breathing-related anaphylaxis symptoms can include:

• Chest tightness
• Difficulty breathing 
• Shortness of breath (dyspnea)
• The sensation of a swollen throat
• Wheezing
  

Skin Symptoms

Anaphylaxis can affect the skin and may cause:

• Flushed appearance and a warm sensation throughout the body
• Hives, or raised red bumps on the skin
• Itchiness 
  

Gastrointestinal (GI) Symptoms

Anaphylaxis symptoms that affect the digestive system can include:

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting 

Cardiovascular Symptoms 

Anaphylaxis symptoms related to the heart can include:

• Dizziness or fainting (syncope) 
• Low blood pressure (hypotension)
• Rapid heartbeat (tachycardia) 

Other Symptoms

Anaphylaxis symptoms may also include:

• Anxiety or an impending sense of doom 
• Slurred speech
• Swelling of the face, lips, tongue, or throat

Causes

Anaphylaxis occurs when the immune system overreacts after exposure to an allergen. The immune system sees the allergen as a threat and releases a flood of chemicals, including histamine, when some people with allergies come into contact with a trigger. These chemicals lead to the characteristic anaphylaxis symptoms.

Allergens known to cause anaphylaxis include:

• Certain foods, such as tree nuts, shellfish, peanuts, milk, and eggs
• High-intensity exercise, especially when paired with temperature or seasonal changes or after eating certain foods 
• Insect stings and bites
• Latex
• Medications, such as penicillin and non-steroidal anti-inflammatory drugs (NSAIDs)

Risk Factors

Not everyone with allergies will go into anaphylaxis when exposed to an allergen. Several risk factors can increase the likelihood of anaphylaxis, including:

• A personal history of asthma (especially if not well-controlled, which puts you at a higher risk of having a severe reaction)
• Heart disease
• Past anaphylactic reaction(s)
• Severe or life-threatening allergies
  

Diagnosis

Anaphylaxis is primarily a clinical diagnosis. Healthcare providers evaluate symptoms and medical history to make a diagnosis rather than relying solely on diagnostic tests. They may use tests after treatment to confirm the diagnosis, see what caused the anaphylactic response (if unknown), and develop a comprehensive management plan to prevent future episodes. 

Diagnostic tests can include: 

• Allergy testing: Skin prick allergy testing involves placing a small number of substances (allergens) on the skin and then scratching the skin. This allows the substance to go under the skin's surface. Your skin may become red, swollen, and itchy within minutes if you are allergic to a substance. These symptoms indicate that the immune system has produced allergen-specific IgE antibodies.
• Blood tests: A blood sample taken during or shortly after anaphylaxis allows healthcare providers to measure levels of an enzyme called tryptase. This enzyme is released by immune cells during an allergic reaction. 

What Are the 4 Stages of Anaphylaxis?

There are four stages of anaphylaxis, which occur rapidly during an episode. These stages include:

• Stage 1: This stage includes symptoms that resemble a mild allergic reaction, including a skin rash, itching, hives, and swelling of the skin. It might not be clear you're having an anaphylactic episode.
• Stage 2: Symptoms worsen and involve multiple systems, including the cardiovascular, digestive, and respiratory systems. You may have abdominal pain, nausea, and trouble breathing. It's important to get immediate medical attention.
• Stage 3: Anaphylactic shock can occur during this stage. Your blood pressure drops dangerously low, cutting off blood flow to the organs.
• Stage 4: Anaphylaxis becomes life-threatening. Blood stops circulating, and you might stop breathing.

Some people can also develop a biphasic anaphylactic response. This is a less common occurrence characterized by symptoms returning after the initial reaction has been treated and resolved.

This phase of the allergic response occurs hours after the initial reaction, even up to 72 hours later. Symptoms similar to those experienced in the initial reaction can reoccur. These symptoms are usually milder, though some may experience moderate to severe symptoms. 

Anaphylaxis Treatment

Anaphylaxis is a medical emergency that requires prompt treatment to stop the allergic reaction and prevent life-threatening complications. Epinephrine is the mainstay treatment for anaphylaxis.

Epinephrine is administered via an auto-injector (e.g., EpiPen) as quickly as possible once symptoms develop. Epinephrine constricts blood vessels and relaxes smooth muscles to counteract the immune response associated with anaphylaxis. This treatment helps restore normal breathing, stabilize blood pressure, and relieve body-wide symptoms.

Seek medical attention if your symptoms don't resolve after using epinephrine. You may require further monitoring and need other treatments like: 

• Antihistamines: Medications like Zyrtec (cetirizine) or Allegra (fexofenadine) can relieve itching, hives, and other allergic symptoms caused by histamine release.
• Corticosteroids: Oral or intravenous (IV) corticosteroids, such as prednisone, help reduce inflammation.
• IV fluids: IV fluids can help regulate blood pressure and maintain hydration in cases of severe anaphylaxis.
• Oxygen therapy: Supplemental oxygen helps deliver oxygen to vital organs if breathing difficulties persist. 

Prevention

The best way to prevent anaphylaxis is to identify and avoid specific allergens, especially those that have caused previous reactions. Prevention methods depend on your triggers. You may carefully read food labels, be cautious about cross-contamination, and take precautions to prevent insect stings.

Other ways to prevent anaphylaxis include:

• Carry an epinephrine auto-injector: You must always carry an epinephrine auto-injector and know how to use it correctly if you have severe allergies.
• Develop an anaphylaxis action plan: Work with a healthcare provider to create an individualized emergency action plan that outlines the steps to take during anaphylaxis. This plan may include instructions on recognizing symptoms, administering epinephrine, and seeking immediate medical attention.
• Educate yourself and others: Learn about anaphylaxis, your triggers, and the signs of a reaction. Educate family members, friends, and caregivers on recognizing and responding to anaphylaxis.
• Regular follow-up with a healthcare provider: Regularly visit a healthcare provider (e.g., an allergist) to update your emergency action plan. You can discuss any changes in triggers or allergy management strategies with them.
• Wear medical identification: Wear a medical bracelet or necklace that clearly states the specific allergens or triggers that can cause anaphylaxis. This helps alert others in case of an emergency.

Complications 

Serious health complications can occur if anaphylaxis goes untreated or treatment is delayed. These include:

• Cardiac arrest: Anaphylaxis can cause a rapid or irregular heartbeat, leading to a potential cardiac arrest in severe cases.
• Respiratory failure: Anaphylaxis can cause swelling in the airways, making it difficult to breathe. Respiratory failure can occur in severe cases, which can be life-threatening.
• Shock: A sudden drop in blood pressure may prevent the body's organs from receiving enough blood and oxygen to function properly. Shock can lead to permanent organ damage (e.g., kidney failure).
  

A Quick Review

Severe allergies that put you at risk of anaphylaxis require ongoing management and vigilance to prevent and address potential allergic reactions. Strict avoidance of known triggers is crucial to lowering your risk of anaphylactic reactions. Regular communication with healthcare providers, keeping your medications (e.g., EpiPen) up-to-date, and educating others about allergies and anaphylaxis are essential steps to help you feel prepared if you are exposed to a trigger.

Living with the threat of anaphylaxis can take an emotional toll on many people with severe allergies. You may find it helpful to seek support from healthcare providers, allergy support groups, or a therapist who can help provide valuable coping mechanisms and strategies to manage any anxiety or fear related to potential allergic reactions.

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