Symptoms and Treatment of Anaphylaxis in Infants
Anaphylaxis in infants presents with unique symptoms and requires prompt epinephrine administration as the first-line treatment to reduce mortality and morbidity.
Clinical Presentation of Anaphylaxis in Infants
Classic Symptoms:
- Skin manifestations: itching, redness, hives, or swelling 1
- Respiratory compromise: hoarseness, throat itching, stridor, cough, difficulty breathing, wheezing, cyanosis 1
- Cardiovascular symptoms: tachycardia, weak pulse, dizziness, collapse, hypotension 1
- Gastrointestinal symptoms: nausea, crampy abdominal pain, vomiting, diarrhea 1
Unique Infant-Specific Presentations:
- Non-classical signs such as ear pulling, tongue thrusting, fussiness, and increased clinginess to caregiver 2
- Behavioral changes specific to infants 1
- Hypotonia (collapse) 1
- Incontinence 1
Diagnostic Criteria:
Anaphylaxis is likely when any one of these three criteria is met:
- Acute onset with skin/mucosal involvement PLUS respiratory compromise OR reduced blood pressure
- Two or more of the following occurring rapidly after allergen exposure: skin/mucosal involvement, respiratory compromise, reduced blood pressure, persistent gastrointestinal symptoms
- Reduced blood pressure after exposure to a known allergen 1
Common Triggers in Infants
- Foods (especially peanut, tree nuts, milk, eggs, crustacean shellfish, and finned fish) are the most common triggers 1
- Insect stings 1
- Medications such as antibiotics 1
- Vaccines rarely trigger anaphylaxis 1
Treatment Algorithm for Infant Anaphylaxis
First-Line Treatment:
- Epinephrine is the first-line treatment and should be administered immediately via intramuscular injection in the mid-outer thigh (vastus lateralis muscle) as soon as anaphylaxis is recognized 1, 3
- For infants, the recommended dose is 0.01 mg/kg of 1:1000 solution 3
- For infants weighing >7.5 kg but <15 kg, the 0.15 mg epinephrine auto-injector is recommended despite being a higher dose than calculated 1, 4
- For infants ≤7.5 kg, the 0.15 mg dose is still recommended given the lack of suitable alternatives, as the benefits outweigh the risks 1, 4
Administration Technique:
- Intramuscular route in the lateral thigh is preferred over subcutaneous due to more favorable pharmacokinetics 3, 5
- Epinephrine can be repeated every 5-15 minutes if symptoms persist 1, 3
Adjunctive Treatments (after epinephrine):
- H1 antihistamines (diphenhydramine 1-2 mg/kg, maximum 50 mg) for cutaneous symptoms 1, 6
- H2 antihistamines may be added 1, 6
- Bronchodilators (albuterol) for persistent respiratory symptoms 1
- Supplemental oxygen as needed 1
- IV fluids for hypotension 1
- Place infant in recumbent position with lower extremities elevated if tolerated 1
Post-Anaphylaxis Management
- All infants who receive epinephrine should be transported to an emergency facility for observation 1
- Observation period of 4-6 hours is reasonable for most patients 1
- Prolonged observation or hospital admission is appropriate for severe or refractory symptoms 1
Discharge Plan
All infants who have experienced anaphylaxis should be sent home with:
- An anaphylaxis emergency action plan 1
- An epinephrine auto-injector (2 doses) 1
- A plan for monitoring auto-injector expiration dates 1
- A plan for arranging further evaluation 1
- Education for caregivers about anaphylaxis recognition and first-aid treatment 1
Important Considerations and Pitfalls
- Fatal anaphylaxis is often associated with delayed use or improper dosing of epinephrine 1
- There are no absolute contraindications to epinephrine use in anaphylaxis, even in high-risk patients 3
- Antihistamines should never replace epinephrine as first-line treatment 6
- Cofactors that may lower the threshold for anaphylaxis include fever, upper respiratory tract infections, and emotional stress 1
- The clinical criteria for anaphylaxis have not yet been validated in infants, making diagnosis challenging 1
- Non-classical signs of infant anaphylaxis can mimic normal infant behavior, complicating diagnosis 2