Pharmacology, Toxicology and Addiction MedicineTier 2Approach to a presentation

Poisonings - insect stings

Red flags

Signs of anaphylaxis (airway swelling, wheeze, hypotension, widespread urticaria with systemic symptoms) require immediate adrenaline and emergency management
Multiple simultaneous stings (swarm attack) carry a risk of direct venom toxicity even without an allergic mechanism, given the cumulative venom load

Differential by mechanism

Localised reaction (pain, swelling, redness confined to the sting site - the most common presentation)

Large local reaction (swelling extending beyond the immediate sting site, still non-systemic)

Anaphylaxis (IgE-mediated systemic allergic reaction)

Toxic reaction from multiple stings (direct venom toxicity from a high cumulative dose, distinct from an allergic mechanism)

Focused history

Number of stings, timing of symptom onset relative to the sting, prior sting reaction history (relevant to anaphylaxis risk with future stings), known insect venom allergy, symptom progression (localised vs spreading vs systemic)
Airway, breathing, and circulatory symptoms specifically, given the time-critical nature of anaphylaxis recognition

Focused examination

Sting site(s) for local reaction severity and any retained stinger (bee stings, unlike wasp stings, typically leave a barbed stinger requiring removal)
Full anaphylaxis assessment (airway, breathing, circulation, skin) in any patient with more than a localised reaction or with risk factors for a systemic reaction

Investigation strategy

Primarily a clinical diagnosis; serum tryptase can support a retrospective diagnosis of anaphylaxis if drawn appropriately timed after a systemic reaction, relevant to confirming the diagnosis and supporting future allergy referral
Referral for confirmatory insect venom allergy testing after any systemic/anaphylactic reaction, to guide future management including venom immunotherapy consideration

Management

Localised reaction: symptomatic treatment (ice, analgesia, antihistamine), stinger removal if present (scrape rather than squeeze to avoid injecting residual venom)
Anaphylaxis: immediate intramuscular adrenaline, standard anaphylaxis resuscitation protocol, and prescription of an adrenaline auto-injector plus referral for allergy specialist assessment and venom immunotherapy consideration given the risk of a similar or worse reaction with future stings

Traps

Squeezing a retained bee stinger rather than scraping it out - squeezing can inject additional residual venom from the attached venom sac

Underestimating multiple-sting toxic reactions as "just allergic" when they may reflect direct venom toxicity requiring different management/monitoring

Discharging a first-time anaphylaxis patient without an adrenaline auto-injector prescription and allergy referral - future sting reactions carry ongoing anaphylaxis risk

Talk track

"Because you've had a serious allergic reaction to this sting, there's a real chance a future sting could cause the same or worse reaction - I want to prescribe you an adrenaline auto-injector to carry with you, and refer you to an allergy specialist who can test what you're specifically allergic to and discuss whether a de-sensitising treatment would help."

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