Clinical Manifestations of Wasp Stings
Most wasp stings cause simple local reactions (redness, swelling, itching, and pain), but clinicians must recognize the spectrum from large local reactions to life-threatening systemic anaphylaxis and, in cases of multiple stings, toxic multi-organ dysfunction. 1
Local Reactions (Most Common)
The majority of wasp stings produce transient localized reactions that resolve within hours to days 1:
- Redness at the sting site
- Swelling (localized edema)
- Pain (immediate, sharp)
- Itching (pruritus)
These typically require no specific treatment and are of little medical consequence 1.
Large Local Reactions
Large local reactions are IgE-mediated but almost always self-limited, characterized by 1:
- Progressive swelling that increases over 24-48 hours
- Diameter >10 cm extending contiguously from the sting site
- Duration of 5-10 days to fully resolve
- Accompanied by significant itching and pain
Critical pitfall: The extensive swelling and even lymphangitis are caused by mediator release, NOT infection—antibiotics are not indicated unless there is clear evidence of secondary infection, which is commonly misdiagnosed 1.
Systemic Reactions (Anaphylaxis)
Systemic reactions involve manifestations NOT contiguous with the sting site, ranging from mild cutaneous symptoms to life-threatening anaphylaxis 1:
Cutaneous Manifestations
- Generalized urticaria (hives distant from sting)
- Angioedema (deeper tissue swelling)
Respiratory Manifestations
- Bronchospasm (wheezing, chest tightness)
- Upper airway obstruction from tongue/throat swelling
- Laryngeal edema
Cardiovascular Manifestations
- Hypotension and shock
- Cardiac arrhythmias
- Coronary artery spasm
Gastrointestinal Manifestations
- Nausea and vomiting
- Diarrhea
- Abdominal pain
Neurological Manifestations
- Seizures
Important note: Systemic reactions occur in 0.4-0.8% of children and up to 3% of adults, with at least 40 deaths annually in the US from sting-induced anaphylaxis 1.
Toxic Reactions from Multiple Stings
When patients sustain ≥10 stings, toxic venom effects predominate over allergic reactions, causing severe multi-organ dysfunction 2:
Multi-Organ Dysfunction Syndrome (MODS)
Recent case series demonstrate that toxic reactions are the dominant presentation in mass envenomation, not anaphylaxis 2:
- Acute Kidney Injury (AKI): Most prominent manifestation, occurring in 17-21% of hospitalized patients 2, 3
- Rhabdomyolysis: Seen in 24.1% of severe cases 2
- Hemolysis: Occurs in 19.2% of patients 2
- Hepatic injury: Present in 30.1% of cases 2
- Coagulopathy: Affects 22.5% of patients 2
- Acute Respiratory Distress Syndrome (ARDS): Occurs in 15.3% overall, with higher rates (30.6%) in MODS patients 4, 3
Rare but Documented Complications
- Cerebral infarction/stroke: Reported in severe cases with multi-organ dysfunction 5
- Cardiovascular collapse requiring vasopressor support 5
Risk factors for mortality in multiple sting cases include 2:
- High creatinine levels
- Shock
- Oliguria
- Anemia
The in-hospital mortality is 5.1% for severe wasp stings, with most deaths from toxic organ injury rather than anaphylaxis 2.
Delayed Reactions
Delayed symptoms can emerge 3-7 days post-sting, including 6:
- Delayed-onset headaches
- New rashes
- Persistent systemic symptoms
This is particularly important for patients who may not seek immediate follow-up.
Clinical Assessment Algorithm
For single or few stings: Assess for local vs. systemic manifestations
- Local only → Symptomatic care
- Systemic symptoms (urticaria, respiratory, cardiovascular, GI, neurological) → Treat as anaphylaxis with epinephrine
For ≥10 stings: Assume toxic reaction risk
- Monitor for AKI (creatinine, urine output)
- Check for rhabdomyolysis (CK levels)
- Assess liver function
- Monitor for hemolysis
- Watch for ARDS development
- Consider early blood purification therapy if ≥20 stings or delayed presentation (≥4 hours) 2
In older patients (>65 years): Higher MODS risk with independent predictors being advanced age, greater number of stings, longer pre-hospital time, and development of AKI or ARDS 3.