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Anaphylaxis (Severe Allergic Reaction)
Content reviewed against published AAP, ACAAI, NIAID guidelines
Last reviewed:
Anaphylaxis is a severe, life-threatening allergic reaction that can occur within seconds to minutes of exposure to an allergen. It requires immediate epinephrine and emergency medical care. Common triggers in babies include cow's milk, eggs, peanuts, tree nuts, and insect stings.
Immediate actions
- Call 911 immediately
- Administer epinephrine auto-injector (EpiPen Jr) immediately if available — do NOT wait to see if symptoms worsen
- DO NOT: Do NOT wait to see if symptoms get better before giving epinephrine
Step-by-Step Response
Recognize anaphylaxis
Signs include: hives/swelling spreading rapidly, difficulty breathing or swallowing, wheezing or hoarse voice, vomiting/diarrhea with skin symptoms, pale/blue color, sudden limpness or unresponsiveness.
Give epinephrine
Use EpiPen Jr (0.15mg) for babies/children under 30kg. Remove blue safety cap. Press orange tip firmly into outer thigh (through clothing is fine). Hold for 10 seconds. Note the time.
Call 911
Tell dispatcher you have a baby in anaphylaxis. Give your location. Mention if epinephrine was given and when.
Position the baby
If breathing is difficult: hold baby upright. If baby is pale or limp: lay flat with legs slightly elevated. If vomiting: place on side to prevent choking.
Monitor closely
Watch breathing. Note if symptoms improve or worsen. Be prepared to give a second dose of epinephrine in 5-15 minutes if no improvement.
Prepare for second dose
If symptoms persist or return after 5-15 minutes, give a second epinephrine injection in the other thigh.
Begin CPR if needed
If baby becomes unresponsive and stops breathing, begin infant CPR immediately.
Hospital monitoring
Even if symptoms resolve, baby MUST go to the hospital. Biphasic reactions (second wave) can occur 4-12 hours later and can be fatal without monitoring.
What NOT to Do
- ✕Do NOT wait to see if symptoms get better before giving epinephrine
- ✕Do NOT give antihistamines (Benadryl) INSTEAD of epinephrine — antihistamines are too slow for anaphylaxis
- ✕Do NOT make baby sit up or stand if they are dizzy or pale — keep flat
- ✕Do NOT leave baby alone — symptoms can worsen rapidly
- ✕Do NOT give food or water if baby is having difficulty breathing or swallowing
- ✕Do NOT assume the reaction is over — biphasic reactions can occur hours later
When to Seek Help
Call 911 if:
- Any suspected anaphylactic reaction — always call
- Swelling of face, lips, tongue, or throat
- Difficulty breathing, wheezing, or stridor
- Baby becomes pale, limp, or unresponsive
- Hives combined with vomiting or breathing difficulty
- Any reaction after a known allergen exposure in a baby with previous anaphylaxis
Go to ER if:
- After ANY administration of epinephrine — baby must be monitored for 4-6 hours minimum
- Allergic reaction involving more than one body system (skin + breathing, skin + GI)
- Any reaction to a known allergen even if currently mild — can progress rapidly
- Reaction to an insect sting with any swelling beyond the sting site
Call your doctor if:
- Mild allergic reaction (hives only, no breathing issues) after a new food
- After an ER visit for anaphylaxis — to arrange allergy testing and action plan
- To get a prescription for epinephrine auto-injectors
- Baby had a reaction but you are unsure if it was anaphylaxis
Age-Specific Guidance
0-6 months
Anaphylaxis is rare at this age but can occur from cow's milk protein in formula or breast milk. Signs may be subtle: sudden vomiting, hives, lethargy, or breathing changes. EpiPen Jr may be prescribed even for infants.
6-12 months
Risk increases as solid foods are introduced. Common first triggers: egg, cow's milk, peanut. Early introduction of allergens actually reduces allergy risk for most babies. Always introduce new foods when you can monitor for 2 hours.
1-3 years
Toddlers may be exposed to new allergens at daycare or social settings. Ensure all caregivers have access to epinephrine and know how to use it. Insect sting allergies may emerge at this age.
Prevention
- Introduce common allergens early (4-6 months) per AAP guidelines to reduce allergy risk
- Introduce one new allergen at a time and wait 2-3 days before introducing another
- Always have 2 epinephrine auto-injectors available if baby has known allergies
- Create and share an allergy action plan with all caregivers
- Read food labels carefully — look for "may contain" warnings
- Alert daycare, family members, and babysitters about all known allergies
- Carry epinephrine at all times — never leave it in the car (temperature sensitivity)
- Get a medical alert bracelet for babies with confirmed severe allergies
Frequently asked questions
Should I call 911 for anaphylaxis (severe allergic reaction)?
What should I do first?
What should I NOT do?
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Sources
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources
Related Emergency Guides
Bottom line
This is a serious emergency. Always call 911 first, then follow the steps above while help is on the way.
You are doing the right thing by learning what to do in an emergency. Being prepared is one of the best things you can do for your child.