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Toxicology – Bee Stings
Core concept
Bee, wasp, yellow-jacket, and hornet stings cause toxicity by two distinct mechanisms:
- IgE-mediated anaphylaxis – may occur after a single sting in a sensitized patient and is not dose-dependent
- Massive envenomation – direct venom toxicity after numerous stings and is dose-dependent
This distinction is critical:
Single sting + rapid airway/circulatory symptoms → think anaphylaxis
Many stings + delayed systemic organ injury → think massive envenomation
Important Species
Clinically important Hymenoptera include:
- European honey bee (Apis mellifera)
- Africanized honey bee
- Wasps
- Yellow jackets
- Hornets
Africanized bees are dangerous mainly because they:
- Defend colonies aggressively
- Attack in large numbers
- May pursue victims
Their venom is not substantially more potent than ordinary honey-bee venom; the major danger is massive venom delivery from multiple simultaneous stings.
Toxic Dose
Anaphylaxis
One sting can be fatal in a highly sensitized individual.
The severity of an allergic reaction does not depend on the number of stings.
Massive envenomation
Direct systemic toxicity generally requires numerous stings.
Systemic toxic reactions have been described with approximately 50 or more simultaneous bee stings, while several hundred may cause life-threatening toxicity in adults. Children may develop severe toxicity with substantially fewer stings because of their lower body mass.
Pathophysiology
1. Allergic / Anaphylactic Reaction
Venom triggers an IgE-mediated hypersensitivity reaction:
Venom exposure → mast-cell/basophil activation → mediator release → vasodilation + capillary leak + bronchospasm + airway edema
This may rapidly cause:
- Urticaria
- Angioedema
- Bronchospasm
- Hypotension
- Shock
- Airway obstruction
2. Massive Envenomation
Large quantities of venom produce direct cellular and organ toxicity.
Major venom-related complications include:
- Rhabdomyolysis
- Intravascular hemolysis
- Acute kidney injury
- Myocardial injury
- Hepatic injury
- Shock
Acute kidney injury may result from a combination of hypotension, myoglobinuria, hemoglobinuria, and direct tubular venom toxicity.
Clinical Features
Local Reaction
Most stings cause:
- Immediate burning pain
- Erythema
- Local swelling
- Wheal-and-flare reaction
- Pruritus
Large local reactions may produce extensive swelling lasting several days.
Anaphylaxis
Symptoms usually develop rapidly.
Dermatologic
- Generalized urticaria
- Flushing
- Pruritus
- Angioedema
Importantly, anaphylaxis can occur without skin findings.
Airway
- Throat tightness
- Tongue or laryngeal edema
- Hoarseness
- Stridor
- Upper-airway obstruction
Pulmonary
- Chest tightness
- Wheezing
- Bronchospasm
- Respiratory distress
- Hypoxemia
Cardiovascular
- Tachycardia
- Hypotension
- Shock
- Collapse
Severe anaphylaxis may rapidly progress to cardiac arrest.
Gastrointestinal
- Nausea
- Vomiting
- Abdominal cramping
- Diarrhea
Massive Envenomation
Patients may initially have extensive local pain and swelling followed by systemic toxicity.
Possible manifestations include:
- Nausea and vomiting
- Diarrhea
- Generalized weakness
- Headache
- Altered mental status
- Hypotension or cardiovascular collapse
- Rhabdomyolysis
- Hemolysis
- Acute kidney injury
- Hepatic injury
- Myocardial injury
- Coma
Some systemic complications, particularly rhabdomyolysis and acute kidney injury, may worsen over the following 24–48 hours rather than appearing immediately.
Diagnosis
Diagnosis is usually clinical:
History of sting(s) + local findings ± allergic or systemic manifestations
No laboratory testing is usually needed for an uncomplicated local reaction.
Investigations in Systemic Reactions
Consider:
- CBC
- Serum electrolytes
- BUN
- Creatinine
- Glucose
- Creatine kinase
- Liver enzymes
- LDH
- Bilirubin
- Urinalysis
- ECG
If significant respiratory compromise is present:
- Pulse oximetry
- Blood gas when indicated
In massive envenomation, specifically monitor for:
- Rhabdomyolysis
- Hemolysis
- Acute kidney injury
- Hyperkalemia
- Metabolic acidosis
Treatment
Anaphylaxis
1. Epinephrine — First-Line Treatment
Intramuscular epinephrine is the treatment of choice for anaphylaxis.
Give into the anterolateral thigh.
Typical dosing:
- Adults: 0.5 mg IM of 1 mg/mL (1:1000) epinephrine
- Children: approximately 0.01 mg/kg IM, using age/weight-appropriate dosing
If airway, breathing, or circulatory problems persist, repeat IM epinephrine after approximately 5 minutes. Current resuscitation guidance identifies IM epinephrine as first-line treatment; IV epinephrine is reserved for appropriately monitored refractory cases managed by experienced clinicians.
The older source’s routine IV epinephrine bolus regimen should not be used as routine first-line treatment for anaphylaxis.
2. Airway
Assess immediately for:
- Stridor
- Hoarseness
- Tongue swelling
- Progressive facial/neck swelling
Early expert airway management may be necessary because severe edema can make later intubation extremely difficult.
3. Oxygen
Administer high-flow oxygen when there is:
- Respiratory distress
- Hypoxemia
- Shock
- Severe anaphylaxis
4. IV Fluids
Anaphylaxis causes marked vasodilation and capillary leakage.
For hypotension:
- Give rapid isotonic crystalloid
- Repeat according to clinical response
5. Bronchospasm
Persistent wheezing after epinephrine can be treated with an inhaled beta-2 agonist such as albuterol/salbutamol.
Bronchodilators are adjuncts and must not replace epinephrine.
6. Antihistamines
Antihistamines may improve:
- Urticaria
- Pruritus
However:
Antihistamines do not treat airway obstruction or shock and must never delay epinephrine.
Local Reactions
For uncomplicated local pain and swelling:
- Cold compresses
- Elevation when appropriate
- Oral analgesics
- Oral antihistamines for itching
Large local reactions are inflammatory and do not routinely require antibiotics unless there is evidence of secondary infection.
Stinger Removal
Honey bees may leave a barbed stinger and venom sac behind.
Remove a retained stinger as rapidly as possible.
Scraping or flicking it out promptly is reasonable. The important principle is to minimize continued venom delivery rather than delaying removal.
Wasps, hornets, and yellow jackets generally do not leave their stingers behind and may sting repeatedly.
Massive Envenomation
Treatment focuses on:
- Airway and ventilation
- IV fluids
- Hemodynamic support
- Renal monitoring
- Electrolyte management
- Treatment of rhabdomyolysis
- Treatment of hemolysis
- Management of shock
Monitor:
- CK
- Creatinine
- Potassium
- Urine output
- Hemoglobin
- LDH/bilirubin when hemolysis is suspected
Severe acute kidney injury may require renal replacement therapy/dialysis.
Antidote
There is no specific antidote for Hymenoptera venom.
For anaphylaxis, however, epinephrine is the essential life-saving treatment.
Monitoring
Patients with systemic reactions should receive:
- Continuous pulse oximetry
- Cardiac monitoring
- Serial blood pressure measurements
- Repeated airway assessment
After massive envenomation, laboratory monitoring should continue because renal and muscle injury may evolve over 24–48 hours.
Admission
Hospital admission should be considered for:
- Cardiovascular instability
- Persistent airway or pulmonary symptoms
- Severe anaphylaxis
- Recurrent symptoms
- Massive numbers of stings
- Rhabdomyolysis
- Hemolysis
- Acute kidney injury
- Significant electrolyte abnormalities
Severe anaphylaxis or massive envenomation may require ICU care.
Follow-Up After Anaphylaxis
Patients with a systemic allergic reaction should be evaluated for:
- Prescription of an epinephrine autoinjector
- Education about its use
- Allergy/immunology referral
- Consideration of venom immunotherapy
Venom immunotherapy can markedly reduce the risk of recurrent systemic reactions in appropriately selected patients.
Prognosis
Most uncomplicated local reactions resolve without serious consequences.
Anaphylaxis
Can produce:
- Airway obstruction
- Shock
- Cardiac arrest
- Death within minutes
Delayed epinephrine increases the risk of severe outcomes.
Massive Envenomation
Systemic venom effects can cause:
- Rhabdomyolysis
- Hemolysis
- Acute kidney injury
- Myocardial injury
- Multiorgan failure
Prompt aggressive supportive care substantially improves outcome.
Important Pitfalls
1. Waiting for hypotension before giving epinephrine
Anaphylaxis should be treated promptly when significant airway, breathing, or circulatory involvement develops.
2. Giving antihistamines instead of epinephrine
Antihistamines treat skin symptoms but do not reverse life-threatening airway obstruction or shock.
3. Routine IV epinephrine bolus
Routine IV epinephrine boluses for anaphylaxis can cause serious cardiovascular complications.
IM epinephrine is first-line.
4. Assuming one sting cannot be dangerous
A single sting can cause fatal anaphylaxis in a sensitized patient.
5. Assuming multiple stings only cause allergy
Massive envenomation causes direct venom toxicity, including rhabdomyolysis, hemolysis, and renal failure.
6. Missing delayed renal injury
AKI following massive envenomation may become apparent over the next 24–48 hours.
High-Yield Toxicology Pearls
Bee sting toxicity has two major patterns: anaphylaxis and massive envenomation.
Think:
One sting + wheeze/stridor/hypotension → ANAPHYLAXIS
versus
Many stings + rhabdomyolysis/hemolysis/AKI → MASSIVE ENVENOMATION
Key points:
- A single sting can cause fatal anaphylaxis
- Anaphylaxis is IgE-mediated and not dose-dependent
- Massive envenomation is dose-dependent direct venom toxicity
- IM epinephrine is first-line for anaphylaxis
- Adult IM epinephrine dose: 0.5 mg
- Repeat IM epinephrine after about 5 minutes if significant symptoms persist
- Antihistamines are adjuncts only
- Remove retained honey-bee stingers promptly
- Multiple stings can cause rhabdomyolysis, hemolysis, and acute kidney injury
- Systemic toxic complications may worsen over 24–48 hours
- There is no specific venom antidote
- Patients with previous systemic allergic reactions should be considered for an epinephrine autoinjector and venom-allergy evaluation
