What should I do if I ingest organic matter and experience an allergic reaction?

Management of Acute Allergic Reaction to Ingested Organic Matter

Immediately assess the severity of the reaction and administer intramuscular epinephrine 0.3-0.5 mg (adults) or 0.01 mg/kg up to 0.3 mg (children) into the anterolateral thigh if there are any signs of anaphylaxis including respiratory symptoms, hypotension, or persistent gastrointestinal symptoms. 1

Immediate Severity Assessment

Determine if this is a mild reaction (isolated urticaria/itching) versus severe anaphylaxis by looking for: 1, 2

• Respiratory compromise: wheezing, dyspnea, throat tightness, stridor 1
• Cardiovascular involvement: hypotension, tachycardia, syncope, weak pulse 3
• Persistent gastrointestinal symptoms: repetitive vomiting, severe abdominal cramping, diarrhea 1, 2
• Mucosal swelling: tongue swelling, lip swelling, angioedema 1, 4

First-Line Treatment: Epinephrine

Do not delay epinephrine administration to give antihistamines—fatal reactions are associated with delayed epinephrine use. 1

• Administer epinephrine 0.3-0.5 mg intramuscularly in adults or 0.01 mg/kg (maximum 0.3 mg) in children 1
• Inject into the anterolateral thigh (outer mid-thigh), never buttocks or other sites 1
• Epinephrine is indicated for any respiratory symptoms, hypotension, or tongue swelling 1
• This is the only effective first-line treatment for anaphylaxis 5, 1

Supportive Measures

Position the patient recumbent with elevated lower extremities to increase venous return if hypotension is present. 2

Administer intravenous fluid bolus of Ringer's lactate 10-20 mL/kg if there is hypotension or significant vomiting. 1, 2

Adjunctive Medications (Only After Epinephrine)

These should never replace or delay epinephrine: 1

• H1 antihistamines: Diphenhydramine 25-50 mg IV/oral (adults) or 1-2 mg/kg (children), or cetirizine 10 mg for adults 1
• H2 antihistamines: Ranitidine 1-2 mg/kg (maximum 75-150 mg) or famotidine in combination with H1 antihistamines 1
• Corticosteroids: Prednisone 1 mg/kg (maximum 60-80 mg) orally or methylprednisolone IV to prevent biphasic reactions 1, 6

Observation Period

Monitor for biphasic reactions, which can occur up to 6 hours after initial symptom resolution: 5

• Mild reactions (few hives that resolved promptly): observe 2 hours after symptom resolution 5
• Moderate reactions (urticaria/angioedema): observe 4 hours after symptom resolution 5
• Severe reactions or history of biphasic reactions: observe 6+ hours, potentially up to 24 hours 5, 4
• Monitor vital signs every 15 minutes until symptoms resolve 2

Emergency Transport

Call 911 and transport to emergency department immediately after epinephrine administration for continued monitoring, even if symptoms improve. 5, 1

Critical Pitfalls to Avoid

• Never use antihistamines as primary treatment instead of epinephrine for severe reactions 1
• Never delay epinephrine to administer other medications 1
• Never discharge too early—biphasic reactions can occur hours later 5
• Never misdiagnose angioedema as infection and inappropriately prescribe antibiotics 1

Post-Reaction Management

After stabilization and observation: 5, 1

• Prescribe epinephrine auto-injector (2 doses) with proper training on use 1
• Provide written anaphylaxis emergency action plan 5
• Educate on strict allergen avoidance and label reading 5
• Refer to allergist for allergen identification and long-term management 1, 4
• Schedule follow-up within 6-12 months 5
• Advise patient to carry medical alert identification 5

Special Considerations

For patients on beta-blockers: Have glucagon available (20-30 μg/kg in children or 1-5 mg in adults) for refractory hypotension. 1

For persistent grade I reactions: If symptoms persist despite intramuscular epinephrine, consider continuous low-dose intravenous epinephrine infusion under close cardiac monitoring in appropriate settings. 6