Anaphylaxis: Symptoms, Causes & Emergency Treatment

What Is Anaphylaxis?

Anaphylaxis is a severe, systemic allergic reaction that occurs rapidly and can be life-threatening. It involves multiple organ systems - typically the skin, respiratory system, cardiovascular system, and/or gastrointestinal system - and requires immediate treatment with epinephrine and emergency medical care.

Anaphylaxis represents the most severe form of allergic reaction. Unlike milder allergic responses that might only affect one area of the body, anaphylaxis is a whole-body reaction that can quickly become life-threatening if not treated promptly. The word "anaphylaxis" comes from the Greek words meaning "against protection," reflecting how the body's protective immune system paradoxically causes harm.

When someone experiences anaphylaxis, their immune system dramatically overreacts to a substance that is normally harmless. This triggers a massive release of chemicals including histamine and other inflammatory mediators from mast cells and basophils throughout the body. These chemicals cause the characteristic symptoms of anaphylaxis: blood vessels dilate and become leaky, airways narrow and swell, blood pressure drops, and the heart may beat irregularly.

The reaction typically develops within seconds to minutes after exposure to the triggering allergen, though some reactions may take up to several hours to appear. The speed of onset often correlates with severity - faster reactions tend to be more dangerous. Without treatment, severe anaphylaxis can lead to respiratory failure, cardiovascular collapse, and death within minutes.

It's important to understand that anaphylaxis is different from a severe allergic reaction affecting only one system. For example, extensive hives covering the body is a severe allergic reaction, but it becomes anaphylaxis when combined with breathing difficulty or cardiovascular symptoms. This distinction matters because anaphylaxis always requires epinephrine, while some allergic reactions may respond to antihistamines alone.

How Common Is Anaphylaxis?

Anaphylaxis affects approximately 1-2% of the population at some point in their lifetime, and the incidence is increasing worldwide. Emergency department visits for anaphylaxis have risen significantly over the past two decades, particularly in developed countries. Food-related anaphylaxis is the most common cause in children and adolescents, while medications and insect stings are more common triggers in adults.

Despite its potentially life-threatening nature, death from anaphylaxis remains relatively rare when treated promptly. Fatality rates are estimated at 0.5-1 per million population per year. However, these statistics underscore the critical importance of rapid recognition and treatment - delays in administering epinephrine significantly increase the risk of a fatal outcome.

The Difference Between Anaphylaxis and Anaphylactic Shock

These terms are often used interchangeably, but there is a technical distinction. Anaphylaxis refers to the severe allergic reaction itself, while anaphylactic shock specifically describes anaphylaxis accompanied by dangerous drops in blood pressure that compromise blood flow to vital organs. Not all anaphylaxis progresses to shock, but all anaphylaxis should be treated as if it might.

What Are the Symptoms of Anaphylaxis?

Anaphylaxis symptoms include difficulty breathing, swelling of throat and tongue, widespread hives or flushing, rapid or weak pulse, dizziness or fainting, and nausea or vomiting. Symptoms typically appear within minutes and can progress rapidly. Early warning signs often include itching in the palms, soles, and scalp.

Recognizing anaphylaxis quickly is crucial because treatment must begin immediately. Symptoms can affect multiple body systems simultaneously, and the combination of symptoms across different systems is what distinguishes anaphylaxis from a localized allergic reaction. Understanding these symptoms can literally save lives.

The symptoms of anaphylaxis develop rapidly, often within seconds to minutes of exposure to the trigger. In some cases, particularly with food allergies, symptoms may take 30 minutes to two hours to appear. The severity and speed of symptom development can vary, but anaphylaxis should always be treated as an emergency regardless of initial severity - mild symptoms can rapidly progress to life-threatening ones.

Skin and Mucosal Symptoms

Skin symptoms are the most common manifestation of anaphylaxis, occurring in approximately 80-90% of cases. However, it's critical to know that 10-20% of anaphylaxis cases have no skin symptoms at all. The absence of hives does not rule out anaphylaxis.

• Hives (urticaria): Raised, itchy welts that can appear anywhere on the body and often spread rapidly
• Generalized flushing: Widespread reddening of the skin, particularly on the face, neck, and chest
• Angioedema: Swelling of deeper tissues, especially around the eyes, lips, tongue, and throat
• Itching: Often begins in specific areas - palms, soles of feet, and scalp are classic early warning sites
• Tingling sensation: Particularly in the mouth, throat, hands, and feet

Respiratory Symptoms

Respiratory symptoms occur in about 70% of anaphylaxis cases and are among the most dangerous. Airway involvement can progress to complete obstruction and respiratory arrest.

• Throat tightness: Sensation of the throat closing or a lump in the throat
• Hoarse voice: Changes in voice quality due to laryngeal swelling
• Stridor: High-pitched breathing sounds indicating upper airway obstruction
• Wheezing: Whistling sounds during breathing, similar to asthma
• Shortness of breath: Difficulty breathing or feeling like you cannot get enough air
• Coughing: Persistent, repetitive coughing

Cardiovascular Symptoms

Cardiovascular symptoms indicate severe anaphylaxis and represent anaphylactic shock. These symptoms result from widespread blood vessel dilation and fluid leakage, causing blood pressure to drop dangerously.

• Rapid pulse: Heart racing, often over 100 beats per minute
• Weak pulse: Pulse may become weak or thready as blood pressure drops
• Low blood pressure: May cause dizziness, lightheadedness, or confusion
• Fainting (syncope): Loss of consciousness due to inadequate blood flow to the brain
• Pale skin: Especially in combination with other cardiovascular symptoms
• Chest pain: Can occur due to reduced blood flow to the heart

Gastrointestinal Symptoms

Gastrointestinal symptoms occur in approximately 30-45% of anaphylaxis cases and can sometimes be the predominant feature, particularly with food-triggered anaphylaxis.

• Nausea and vomiting: Often severe and sudden onset
• Abdominal pain: Cramping or severe stomach pain
• Diarrhea: May occur during or after the acute reaction
• Difficulty swallowing: Due to throat swelling

Other Symptoms

• Sense of impending doom: An overwhelming feeling that something terrible is about to happen - this is a recognized symptom of anaphylaxis
• Confusion: Due to reduced blood flow to the brain
• Anxiety: Extreme anxiety or agitation
• Loss of consciousness: In severe cases

What Causes Anaphylaxis?

The most common causes of anaphylaxis are food allergies (especially peanuts, tree nuts, shellfish, fish, milk, and eggs), insect stings (bees, wasps, hornets), medications (antibiotics, NSAIDs), and latex. In some cases, the trigger cannot be identified (idiopathic anaphylaxis), and exercise can trigger reactions in susceptible individuals.

Anaphylaxis occurs when the immune system overreacts to a substance (allergen) that is normally harmless. The body has previously been "sensitized" to this allergen - meaning the immune system has encountered it before and produced IgE antibodies against it. When the allergen is encountered again, these antibodies trigger mast cells and basophils to release massive amounts of histamine and other chemicals, causing the symptoms of anaphylaxis.

The specific triggers vary by age and geographic region. In children and adolescents, food is the most common trigger, while in adults, medications and insect stings are more frequent causes. Understanding the common triggers helps with both prevention and rapid recognition of anaphylaxis.

Food Triggers

Food allergies are the leading cause of anaphylaxis outside of hospitals, accounting for approximately 30-50% of all cases. The foods most commonly responsible include:

• Peanuts: The most common cause of fatal food-induced anaphylaxis
• Tree nuts: Walnuts, almonds, cashews, pistachios, and others
• Shellfish: Shrimp, crab, lobster, and other crustaceans
• Fish: Various species including salmon, tuna, and cod
• Milk: Particularly in children
• Eggs: Both egg white and yolk proteins
• Wheat: Less common but can cause severe reactions
• Soy: Found in many processed foods
• Sesame: Increasingly recognized as a major allergen

Insect Stings

Stinging insects from the Hymenoptera order are responsible for significant numbers of anaphylaxis cases, particularly in adults. The main culprits include:

• Honeybees: Leave their stinger behind, continuing to inject venom
• Wasps: Can sting multiple times
• Hornets: Particularly aggressive species
• Yellow jackets: Common in late summer and fall
• Fire ants: Common in certain geographic regions

Medications

Drug-induced anaphylaxis can occur with many medications, both prescription and over-the-counter. Common triggers include:

• Antibiotics: Penicillins and cephalosporins are most common
• NSAIDs: Aspirin, ibuprofen, and others
• Contrast agents: Used in medical imaging
• Anesthetics: Particularly muscle relaxants used during surgery
• Chemotherapy drugs: Various anticancer medications
• Biologics: Monoclonal antibodies and similar treatments

Other Triggers

• Latex: Found in gloves, balloons, and medical equipment
• Exercise: Exercise-induced anaphylaxis, sometimes only when combined with food
• Cold: Cold-induced anaphylaxis from cold water or air
• Seminal fluid: Rare but documented cause
• Idiopathic: No identifiable trigger in 20% of cases

When Should You Call Emergency Services?

Call emergency services immediately if someone has difficulty breathing, throat or tongue swelling, feels faint or loses consciousness, has symptoms affecting multiple body systems, or has used an epinephrine auto-injector. Never wait to see if symptoms improve - anaphylaxis can progress rapidly and unpredictably.

The decision to call emergency services should never be delayed when anaphylaxis is suspected. Time is critical in anaphylaxis treatment, and delays in seeking emergency care significantly increase the risk of a fatal outcome. Studies consistently show that delayed epinephrine administration is the primary factor in anaphylaxis deaths.

When you call emergency services, tell them you suspect anaphylaxis. Describe the symptoms you're observing and mention any known allergies or triggers. If epinephrine has been or will be administered, inform them of this as well. Stay on the line and follow any instructions given by the emergency dispatcher.

Why You Must Still Call After Using Epinephrine

Even if symptoms improve after epinephrine administration, emergency medical care is still essential for several important reasons:

• Biphasic reactions: Up to 20% of anaphylaxis cases have a second wave of symptoms that can occur 1-72 hours after the initial reaction, even without re-exposure to the allergen
• Epinephrine effects are temporary: The effects of epinephrine wear off within 15-20 minutes, and symptoms may return
• Additional treatment may be needed: You may require IV fluids, additional medications, or monitoring
• Medical observation: Healthcare providers should observe you for at least 4-6 hours after anaphylaxis

How Is Anaphylaxis Treated?

Epinephrine (adrenaline) is the first-line treatment for anaphylaxis and should be administered immediately via intramuscular injection into the outer thigh. This is followed by calling emergency services, positioning the patient appropriately, and providing supportive care. Additional treatments include antihistamines, corticosteroids, bronchodilators, and IV fluids.

The treatment of anaphylaxis follows a clear priority: epinephrine first, everything else second. No other medication can substitute for epinephrine in treating anaphylaxis. Antihistamines, while helpful for allergic reactions, cannot reverse the life-threatening cardiovascular and respiratory effects of anaphylaxis. This is why all major medical organizations worldwide emphasize epinephrine as the essential first treatment.

Epinephrine: The Life-Saving Treatment

Epinephrine (also called adrenaline) works by rapidly reversing the dangerous effects of anaphylaxis. It constricts blood vessels to raise blood pressure, relaxes airway muscles to improve breathing, reduces swelling, and increases heart output. These effects begin within minutes of administration.

Epinephrine should be injected into the outer middle portion of the thigh. This can be done through clothing if necessary - do not waste time removing pants or tights. The auto-injector should be held firmly against the thigh for at least 10 seconds to ensure the full dose is delivered.

What to Do While Waiting for Emergency Services

After administering epinephrine and calling emergency services, take these additional steps:

• Position the person appropriately: If having trouble breathing, help them sit up. If feeling faint or showing signs of shock, lie them down with legs elevated (unless this worsens breathing)
• Remove the trigger if possible: If an insect stinger is visible, scrape it off with a fingernail or card edge - don't squeeze it
• Monitor breathing: Be prepared to perform CPR if the person stops breathing or has no pulse
• Give a second epinephrine dose: If symptoms don't improve within 5-15 minutes, a second dose may be given
• Give additional medications if available: Antihistamines and bronchodilators (for those with asthma) can help but should not replace epinephrine
• Note the time: Record when symptoms started and when epinephrine was given
• Stay calm: Your calm demeanor will help the affected person

Hospital Treatment

Once at the hospital, treatment may include:

• Additional epinephrine: IV or intramuscular doses as needed
• IV fluids: To restore blood pressure and treat shock
• Antihistamines: Both H1 blockers (like diphenhydramine) and H2 blockers
• Corticosteroids: To reduce inflammation and prevent delayed reactions
• Bronchodilators: For persistent wheezing
• Oxygen: If blood oxygen levels are low
• Vasopressors: For persistent low blood pressure
• Monitoring: Observation for at least 4-6 hours, longer for severe reactions

How Can You Prevent Anaphylaxis?

Prevention involves strict avoidance of known triggers, carrying epinephrine auto-injectors at all times, wearing medical identification, having a written anaphylaxis action plan, and informing others about your allergy. Allergen immunotherapy may reduce sensitivity in some cases, particularly for insect venom allergies.

For people who have experienced anaphylaxis or are at risk, prevention is a daily practice. Complete avoidance of triggers is ideal but not always possible, which is why being prepared to treat a reaction is equally important. The combination of avoidance strategies and emergency preparedness provides the best protection.

Avoiding Triggers

For food allergies:

• Read all food labels carefully - allergens can be hidden in unexpected products
• Ask about ingredients when eating at restaurants or other people's homes
• Be aware of cross-contamination risks in food preparation
• Carry safe snacks to avoid situations where allergen-free food isn't available
• Learn the different names for your allergen (e.g., casein for milk protein)

For insect sting allergies:

• Avoid wearing bright colors and floral patterns outdoors
• Don't wear perfumes or scented products outside
• Be cautious around food and drinks outdoors - insects are attracted to sweet foods
• Wear shoes outdoors, especially in grassy areas
• Stay calm and move away slowly if insects approach
• Consider venom immunotherapy, which is highly effective (90-95% protection)

For medication allergies:

• Inform all healthcare providers about your allergies
• Wear medical identification listing your drug allergies
• Verify medications before taking them, especially when receiving new prescriptions
• Ask about pre-medication protocols if you need contrast agents

Being Prepared

• Always carry two epinephrine auto-injectors: Keep them accessible at all times - not in luggage, lockers, or cars in extreme temperatures
• Check expiration dates: Replace auto-injectors before they expire
• Know how to use your auto-injector: Practice with a trainer device regularly
• Wear medical identification: Bracelets or necklaces alert others to your allergy if you cannot communicate
• Have an anaphylaxis action plan: A written document explaining your triggers, symptoms, and treatment steps
• Educate family, friends, and colleagues: They should know how to recognize anaphylaxis and use your auto-injector

What First Aid Should You Give for Anaphylaxis?

First aid for anaphylaxis involves recognizing the signs, calling emergency services, administering epinephrine, positioning the person correctly, and being prepared to perform CPR if needed. Stay calm, act quickly, and never leave the person alone until emergency services arrive.

If you witness someone having anaphylaxis, your quick action could save their life. Even if you're not certain it's anaphylaxis, it's better to act and be wrong than to wait and watch the situation deteriorate. Epinephrine is safe to give even if the reaction turns out not to be anaphylaxis.

Step-by-Step First Aid

1. Recognize the signs: Multiple symptoms affecting different body systems, rapid onset, known allergy exposure
2. Call emergency services immediately: Don't wait to see if symptoms improve
3. Help the person use their epinephrine: If they have an auto-injector, help them use it or administer it yourself
4. Position appropriately:
   • If having trouble breathing: help them sit up
   • If showing signs of shock (pale, faint): lie them down with legs elevated
   • If unconscious but breathing: recovery position
   • If pregnant: lie on left side
5. Remove the trigger if possible: Scrape out bee stinger, move away from source
6. Give a second epinephrine dose: If no improvement after 5-15 minutes
7. Start CPR if needed: If the person stops breathing or has no pulse
8. Keep them calm and warm: Cover with a blanket if available
9. Stay with them: Until emergency services arrive

What Happens After Anaphylaxis?

After anaphylaxis, you'll be monitored in hospital for at least 4-6 hours for biphasic reactions. You'll receive a prescription for epinephrine auto-injectors, may be referred to an allergist for testing, and should develop an anaphylaxis action plan. Follow-up care is essential for long-term management and prevention.

Recovery from anaphylaxis involves both immediate medical care and long-term planning. The immediate concern is monitoring for biphasic reactions, but equally important is preparing for future prevention and ensuring you have the tools and knowledge to manage your risk.

Hospital Observation

After the acute reaction is controlled, you'll typically be observed for at least 4-6 hours. Those with severe reactions, respiratory symptoms, or risk factors may need overnight observation. During this time, healthcare providers will monitor for:

• Return of symptoms (biphasic reaction)
• Vital signs including blood pressure and heart rate
• Breathing and oxygen levels
• Overall clinical status

Before Leaving the Hospital

Before discharge, you should receive:

• Prescription for at least two epinephrine auto-injectors
• Education on how to use the auto-injectors
• Written anaphylaxis action plan
• Information about avoiding triggers
• Referral to an allergist for follow-up
• Corticosteroids for 2-3 days (in some cases)

Long-Term Management

After experiencing anaphylaxis, work with an allergist to:

• Identify the trigger through allergy testing
• Develop a comprehensive avoidance plan
• Consider allergen immunotherapy if appropriate (particularly effective for venom allergies)
• Address any underlying conditions that increase risk
• Review and update your action plan annually