Allergic Reactions and Anaphylaxis: How to Use an EpiPen and When to Call 911
Anaphylaxis can kill in minutes. An epinephrine auto-injector buys time — but only if someone nearby knows how to use it.
If someone has signs of anaphylaxis (a reaction in two or more body systems after exposure — e.g. hives plus trouble breathing): (1) give epinephrine without delay — press the auto-injector’s orange tip firmly into the middle of the outer thigh until it clicks; (2) call 911; (3) keep the person lying down with legs raised (sit them up if they’re struggling to breathe, and never stand them up); (4) if symptoms don’t improve in about 5 minutes, give a second dose. Epinephrine is first-line — don’t wait to try an antihistamine or inhaler instead.
Mild vs. Severe Allergic Reactions
Mild to Moderate Reaction
A mild reaction typically involves one body system: hives or a rash, itching in the mouth, a runny nose, mild nausea, or localised swelling around the contact site. These are uncomfortable but not immediately life-threatening and can usually be managed with an antihistamine. Watch closely — a mild reaction can progress.
Severe Reaction (Anaphylaxis)
Anaphylaxis involves two or more body systems and escalates rapidly. It is a medical emergency.
The critical distinction: a mild reaction stays local. Anaphylaxis goes systemic. If there is any doubt, treat it as anaphylaxis. Using epinephrine on someone who does not need it usually causes only a fast heartbeat and shakiness for a few minutes; not using it on someone who does need it can be fatal.
Source: Canadian Red Cross (2025); recognition rests on signs in two or more body systems after exposure, per ILCOR 2025.
How to Use an EpiPen: Step by Step
- Recognise the emergency. If someone with a known allergy shows signs of anaphylaxis after exposure, act immediately.
- Call 911 or have someone call while you prepare the auto-injector.
- Locate the auto-injector. Check the person’s bag, backpack, or emergency kit. Use it even if slightly expired — some epinephrine is better than none.
- Remove the blue safety cap. Pull straight off. “Blue to the sky.”
- Position the orange tip down. Hold in your fist. “Orange to the thigh.”
- Inject into the outer thigh. Press firmly into the middle of the outer thigh until you hear a click. You can inject through clothing.
- Hold in place for 3 seconds (newer models) or 10 seconds (older models) — follow the instructions printed on your device.
- Remove and massage the injection site for about 10 seconds to aid absorption.
- Note the time. Paramedics will need this information.
- Position the person. Keep them lying down with legs raised. Sit them up if they are struggling to breathe; turn them on their side if vomiting. Do not stand them up.
Source: intramuscular epinephrine in the outer (lateral) thigh is the primary treatment regardless of trigger — Canadian Red Cross / Heart & Stroke (aligned with AHA 2024 and ILCOR 2025). Always follow the instructions on your specific auto-injector.
Common Triggers of Anaphylaxis
Food Allergies (Most Common in Children)
- Peanuts and tree nuts — among the most common triggers of fatal food-induced anaphylaxis
- Milk and eggs — common in younger children; many outgrow these
- Shellfish, fish, wheat, soy, sesame, and mustard — all are priority allergens that must be labelled on packaged food in Canada (Health Canada); sesame is a rising concern
Insect Stings
Bee, wasp, and hornet stings are another common cause. A person may react mildly to one sting and severely to the next. Read our guide on bee stings and bug bites first aid.
Biphasic Reactions: Why the Hospital Matters
After the first dose of epinephrine wears off, some people experience a biphasic reaction — a second wave of symptoms hours later, even without further exposure. This second wave can be just as severe. That is why anyone treated for anaphylaxis needs urgent medical assessment and a period of monitoring, even if the auto-injector worked and they feel fine. Follow the observation period your treating clinician or local emergency service advises.
Managing Allergies at School
- Anaphylaxis action plan on file at school and with every caregiver
- Auto-injector accessible — with the child or immediately nearby, not locked in an office
- Train caregivers — a Life Safe first aid course includes hands-on auto-injector training
- Teach your child to self-advocate — see our guide on teaching kids about emergencies
- MedicAlert identification for first responders
Why First Aid Training Matters
In a Life Safe first aid course, you physically practise administering an auto-injector, learn to distinguish anaphylaxis from a mild reaction, and understand how anaphylactic shock can lead to cardiac arrest — making CPR skills essential.
Frequently Asked Questions
What are the signs of anaphylaxis?
Anaphylaxis typically involves two or more body systems reacting simultaneously. Signs include skin reactions (hives, flushing, swelling), breathing difficulties (wheezing, throat tightness), cardiovascular symptoms (dizziness, fainting, weak pulse), and gastrointestinal symptoms (nausea, vomiting). If someone with a known allergy shows any of these signs, treat it as anaphylaxis (Canadian Red Cross).
How do you use an EpiPen?
Remove the blue safety cap. Hold firmly with the orange tip down. Press into the middle of the outer thigh until you hear a click. Hold for 3 seconds (or 10 on older models). Remove and rub the site for about 10 seconds. Call 911 and note the time.
Should I call 911 after using an EpiPen?
Yes, always. Symptoms can return after the first dose wears off (a biphasic reaction), so anyone treated for anaphylaxis needs urgent medical assessment and monitoring — even if they feel better.
When do you give a second dose?
If symptoms don’t improve about 5 minutes after the first dose, give a second one (ILCOR 2025 / European Resuscitation Council). Most people carry two auto-injectors for this reason.
Can you give an EpiPen to someone else’s child?
Yes. Good Samaritan laws in Ontario protect people who provide emergency assistance in good faith. The risk of not using it far outweighs the risk of using it.
What is the most common cause of anaphylaxis in children?
Food allergies are the most common trigger. Canada’s priority labelled allergens include peanuts, tree nuts, milk, eggs, wheat, soy, fish, shellfish, sesame, and mustard (Health Canada). Insect stings are another common cause.
Sources & medical review
Reviewed by Milos Radojcic (Canadian Red Cross / Heart & Stroke / Lifesaving Society First Aid & CPR Instructor, 10+ yrs). Clinical content aligned with the Canadian Red Cross, the Heart & Stroke Foundation of Canada, the 2025 ILCOR First Aid consensus and the European Resuscitation Council (epinephrine in the outer thigh; second dose if symptoms persist at ~5 minutes), the AHA 2024 first aid guidelines, and Health Canada (priority food allergens). Last reviewed July 2026.