Overview
Anaphylaxis is a severe, potentially life-threatening allergic reaction that occurs rapidly and affects multiple body systems. It is a medical emergency that requires immediate treatment with epinephrine (adrenaline) and emergency medical care.
During anaphylaxis, the immune system releases a flood of chemicals that can cause blood pressure to drop suddenly and airways to narrow, blocking breathing. Common triggers include certain foods, insect stings, medications, and latex. Anaphylaxis can occur within seconds or minutes of exposure to an allergen and can progress rapidly if not treated promptly.
With prompt recognition and appropriate treatment, most people recover fully from anaphylaxis. However, without immediate intervention, anaphylaxis can be fatal. Carrying an epinephrine auto-injector and knowing how to use it is essential for anyone at risk.
Symptoms
Symptoms of anaphylaxis develop rapidly and may include:
Skin reactions:
• Hives, itching, and flushed or pale skin
• Swelling of the lips, tongue, or throat
Respiratory symptoms:
• Difficulty breathing, wheezing, or noisy breathing
• Sensation of throat tightness or lump in the throat
• Coughing or hoarseness
Cardiovascular symptoms:
• Dizziness, lightheadedness, or fainting
• Rapid or weak pulse
• Low blood pressure (hypotension)
Gastrointestinal symptoms:
• Nausea, vomiting, or diarrhea
• Abdominal pain or cramping
Other symptoms:
• A feeling of impending doom or anxiety
• Confusion or slurred speech
• Loss of consciousness
• Cardiac arrest in severe cases
Causes
Anaphylaxis is triggered by an overreactive immune system in response to a harmless substance (allergen). Common triggers include:
Foods:
• Peanuts and tree nuts (walnuts, pecans, almonds, cashews)
• Shellfish (shrimp, lobster, crab)
• Fish
• Eggs
• Milk and dairy products
• Wheat, soy, and sesame
Insect stings:
• Bee stings
• Wasp, hornet, and yellow jacket stings
• Fire ant bites
Medications:
• Penicillin and other antibiotics
• Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin
• Anesthetics
• Chemotherapy drugs
Other triggers:
• Latex (natural rubber)
• Exercise (exercise-induced anaphylaxis)
• Alcohol or certain medications may worsen reactions
• In some cases, the cause remains unknown (idiopathic anaphylaxis)
Treatment
Anaphylaxis is a medical emergency. Immediate treatment is essential:
Emergency treatment:
• Epinephrine (adrenaline) injection — the first-line treatment. Use an auto-injector (e.g., EpiPen, Jext, Emerade) immediately into the outer thigh.
• Call emergency services (911/112/108) right away — even if symptoms improve.
• Lie flat with legs elevated to maintain blood flow to vital organs. If breathing is difficult, allow sitting upright. Do not stand or walk.
• A second dose of epinephrine may be needed after 5–15 minutes if symptoms persist.
Hospital treatment may include:
• Oxygen therapy to support breathing
• Intravenous fluids to raise blood pressure
• Antihistamines and corticosteroids to reduce inflammation
• Bronchodilators to open airways
• Continuous monitoring for biphasic reactions (recurrence of symptoms hours later)
Long-term management:
• Avoid known allergens
• Carry an epinephrine auto-injector at all times
• Wear a medical alert bracelet
• Work with an allergist to create an emergency action plan
• Consider allergy testing and immunotherapy (allergy shots) where appropriate