What symptoms warrant the use of an EpiPen (epinephrine)?

When to Use an EpiPen for Anaphylaxis

An EpiPen should be used immediately at the first signs of anaphylaxis, particularly when respiratory or cardiovascular symptoms are present, or when there is known exposure to an allergen that previously caused anaphylaxis, even if symptoms are still mild. 1, 2

Primary Indications for EpiPen Use

• Respiratory symptoms: Difficulty breathing, wheezing, shortness of breath, throat tightness, or stridor 1
• Cardiovascular symptoms: Hypotension, dizziness, fainting, or loss of consciousness 1, 2
• Skin manifestations with other systemic symptoms: Widespread hives (urticaria), flushing, itching, or angioedema, especially when accompanied by symptoms affecting other organ systems 1
• Gastrointestinal symptoms: Severe abdominal pain, persistent vomiting, or diarrhea, particularly when occurring with other symptoms 1, 2
• Known allergen exposure in someone with previous anaphylaxis, even if symptoms are initially mild 1

Special Circumstances Requiring Immediate EpiPen Use

• Generalized acute urticaria after exposure to a known allergen that previously triggered anaphylaxis 1
• Symptoms after insect sting in someone with previous systemic reactions, even if initially only skin symptoms are present 1
• Rapid progression of symptoms after exposure to foods commonly associated with severe reactions (peanuts, tree nuts, seafood, milk) 1
• Any symptoms in someone with asthma and known severe allergies, as they are at higher risk of fatal anaphylaxis 1, 2

Decision-Making Algorithm

1. Has there been exposure to a known allergen trigger?

   • If YES and previous anaphylaxis to this trigger → Use EpiPen immediately 1
   • If YES but no previous anaphylaxis → Proceed to symptom assessment

2. Are any of these symptoms present?

   • Difficulty breathing, wheezing, or throat tightness
   • Dizziness, fainting, or low blood pressure
   • Widespread hives with any other systemic symptoms
   • Severe abdominal pain, persistent vomiting
   • If YES to ANY → Use EpiPen immediately 1, 2

3. Special risk factors present?

   • Asthma with allergic reaction
   • Previous severe reactions
   • Exposure to high-risk allergen (peanuts, tree nuts, seafood)
   • If YES → Lower threshold to use EpiPen 1, 2

Common Pitfalls to Avoid

• Waiting too long: Delaying epinephrine administration is associated with increased mortality and morbidity 2, 3
• Relying on antihistamines or inhalers: These are not substitutes for epinephrine in anaphylaxis 1, 4
• Assuming mild symptoms will remain mild: Anaphylaxis can progress rapidly and unpredictably 1, 5
• Fear of using the EpiPen: The risks of untreated anaphylaxis far outweigh the risks of appropriate epinephrine use 1, 6
• Improper injection technique: Inject into the outer thigh muscle, not into buttocks, hands, or feet 6

When in Doubt

• If uncertain whether symptoms represent anaphylaxis, err on the side of using the EpiPen 1
• Even experienced physicians cannot predict which reactions will remain mild and which will become life-threatening 1
• After using an EpiPen, seek immediate medical attention as symptoms may return and additional treatment may be needed 1, 7

Administration Considerations

• Inject into the anterolateral thigh (vastus lateralis muscle) for optimal absorption 2, 6
• If symptoms do not improve or worsen after 5-15 minutes, a second dose may be necessary 7, 3
• Position the person lying flat with legs elevated if experiencing dizziness or low blood pressure, unless they are having breathing difficulties 1

Remember that epinephrine is the first-line treatment for anaphylaxis, and there is no contraindication to using epinephrine when anaphylaxis is suspected 1, 2.