10.4 Hymenoptera Stings, Ticks, and Other Arthropods
Key Takeaways
- Hymenoptera stings kill through anaphylaxis rather than venom volume, and intramuscular epinephrine into the anterolateral thigh (0.3 to 0.5 mg in adults, 0.01 mg/kg in children) is the first and most important intervention.
- A large local reaction can exceed 10 cm and last several days without indicating systemic allergy, so it is treated with cold compresses, analgesics, antihistamines, and sometimes a short steroid course rather than with epinephrine.
- Honeybees leave a barbed stinger that should be removed promptly by any method, since speed matters more than technique, while wasps, hornets, and fire ants can sting repeatedly.
- Massive envenomation from hundreds of stings produces a toxic syndrome with vomiting, hemolysis, rhabdomyolysis, kidney injury, and coagulopathy that requires hospitalization even without allergy.
- Other arthropods have distinctive presentations: tick paralysis resolves after tick removal, alpha-gal sensitization causes delayed red meat allergy, puss caterpillar contact causes intense pain with a gridlike lesion, and blister beetles contain cantharidin that causes vesication and hematuria.
The Order Hymenoptera
| Family | Members | Sting Behavior | Venom Notes |
|---|---|---|---|
| Apidae | Honeybees, bumblebees | Honeybee leaves a barbed stinger with venom sac, stings once and dies | Melittin, phospholipase A2, hyaluronidase, apamin |
| Vespidae | Yellow jackets, hornets, paper wasps | Smooth stinger, stings repeatedly; yellow jackets are aggressive scavengers around food and trash | Antigen 5, phospholipase, hyaluronidase; extensive cross-reactivity within the family |
| Formicidae | Imported fire ants, harvester ants | Anchor with mandibles and sting repeatedly in a circular pattern | Piperidine alkaloids produce the characteristic sterile pustule at 24 hours |
Africanized honeybees are not more venomous per sting; they are far more defensive, attack in large numbers, and pursue over long distances, which converts an allergy problem into a massive envenomation problem.
Classifying the Reaction
| Reaction | Findings | Management |
|---|---|---|
| Local | Pain, wheal, and redness within a few centimeters, resolving in hours | Cold compress, oral analgesic, antihistamine if itching; home care |
| Large local | Contiguous swelling that can exceed 10 cm and peaks at 24 to 48 hours, sometimes lasting a week; may involve a whole limb | Cold compresses, elevation, analgesics, antihistamines, and a short oral steroid course for severe swelling. Not an indication for epinephrine, and it predicts only a small increase in future systemic risk |
| Systemic allergic (anaphylaxis) | Urticaria beyond the sting site, angioedema, wheeze or stridor, vomiting, hypotension, syncope, usually within 15 to 30 minutes | Intramuscular epinephrine immediately, airway support, fluids, adjunctive antihistamines and steroids |
| Toxic (massive envenomation) | Dozens to hundreds of stings: vomiting, diarrhea, fever, hemolysis, rhabdomyolysis, kidney injury, coagulopathy, seizures | Hospitalization, aggressive fluids, monitoring of creatine kinase, potassium, hemoglobin, and kidney function |
| Delayed or unusual | Serum sickness at 7 to 14 days, or rarely neurologic or vasculitic syndromes | Symptomatic; allergy referral |
Epinephrine: The Only Intervention That Reverses Anaphylaxis
- Dose: 0.3 to 0.5 mg of 1 mg/mL epinephrine intramuscularly into the anterolateral thigh in adults; 0.01 mg/kg (maximum 0.3 to 0.5 mg) in children. Repeat every 5 to 15 minutes as needed.
- Antihistamines and steroids treat hives and may reduce the chance of protracted symptoms, but they do not reverse airway edema or shock, and waiting for them is a classic fatal error.
- Patients on beta-blockers may respond poorly and may need glucagon in addition to epinephrine.
- Disposition: observe after anaphylaxis for several hours because of the possibility of a biphasic reaction, prescribe two epinephrine autoinjectors with demonstration, and refer to an allergist for testing and consideration of venom immunotherapy, which reduces the risk of future systemic reactions to roughly 5% or less.
Stinger Removal
For a honeybee sting, remove the stinger promptly. Scraping versus pinching matters far less than speed, because venom continues to be injected while the sac remains attached. Then wash the site, apply a cold compress, and update tetanus status if indicated.
Other Arthropods on the Official Topic List
Ticks
| Syndrome | Features | Management |
|---|---|---|
| Tick paralysis | Ascending flaccid paralysis with areflexia, most often in children with an engorged tick in the scalp hair; caused by a salivary neurotoxin | Find and remove the tick; recovery usually begins within hours to a day or two. In Australian Ixodes holocyclus paralysis, removal may be followed by transient worsening |
| Alpha-gal syndrome | Lone star tick bites sensitize to galactose-alpha-1,3-galactose, producing delayed anaphylaxis 3 to 6 hours after eating red meat | Avoidance, epinephrine autoinjector, allergy referral |
| Tick-borne infection | Lyme disease, Rocky Mountain spotted fever, anaplasmosis, ehrlichiosis, babesiosis, tularemia, Powassan virus | Removal with fine-tipped forceps close to the skin, steady traction, no burning or petroleum jelly; educate about rash and fever and refer as appropriate |
Caterpillars and Moths
- Puss caterpillar (Megalopyge opercularis): intense burning pain with a characteristic gridlike or tram-track erythematous lesion, sometimes with regional lymphadenopathy and systemic symptoms. Remove spines with adhesive tape, then use cold compresses and analgesia.
- Saddleback and io moth caterpillars: painful urticating spines.
- Browntail and gypsy moth hairs: pruritic dermatitis and occasionally respiratory irritation.
- Lonomia species (South America): a true hemorrhagic syndrome with consumption coagulopathy requiring antivenom where available.
Beetles, Centipedes, Millipedes, and Mites
| Organism | Effect | Management |
|---|---|---|
| Blister beetles (Epicauta, Spanish fly) | Cantharidin causes vesicant skin lesions; ingestion causes gastrointestinal burns, hematuria, and kidney injury, with priapism historically | Irrigation, wound care; hospital evaluation for ingestion |
| Centipedes (Scolopendra) | Paired puncture wounds with intense pain, local swelling, rarely lymphangitis | Local care, analgesia, hot or cold application, tetanus update |
| Millipedes | Secrete benzoquinones causing skin staining and conjunctival irritation | Copious irrigation, especially for eye exposure |
| Chiggers and scabies mites | Intense pruritus with papules; scabies has burrows and household spread | Permethrin for scabies, antipruritics for chiggers |
| Bed bugs | Linear grouped pruritic papules | Symptomatic care, environmental control |
| Fleas | Pruritic papules, usually on the lower legs | Symptomatic care, pet treatment |
Wound Care and Infection
Any arthropod bite or sting can become secondarily infected. Advise the caller to watch for expanding redness after 24 to 48 hours, warmth, purulent drainage, fever, or a red streak, and to seek care if those appear. A honeybee or fire ant pustule is not infection and should be left intact.
Poison Center Case: Stings at the Woodpile
A 46-year-old man disturbs a yellow jacket nest while stacking firewood and is stung more than a dozen times on the arms and neck. Ten minutes later his wife calls: he has hives over his chest, his voice sounds hoarse, he is wheezing, and he feels faint.
Specialist actions. The CSPI recognizes anaphylaxis and directs the caller to use the epinephrine autoinjector now into the outer thigh if one is available, then to call 911 immediately and lay the patient flat with the legs elevated unless he is vomiting or short of breath sitting up. The specialist stays on the line, advises a repeat epinephrine dose after 5 minutes if breathing does not improve, and explains that antihistamines are an adjunct and not a substitute. The receiving emergency department is notified. After stabilization, discharge planning includes observation for a biphasic reaction, two autoinjectors with a demonstration, written instructions to use them before antihistamines, avoidance counseling, and referral for venom immunotherapy. Because he also received many stings, the team monitors creatine kinase, kidney function, and urine for hemoglobin.
A 9-year-old stung on the forearm by a yellow jacket develops 14 cm of contiguous swelling and redness over 24 hours, with itching but no hives elsewhere, no wheeze, and normal vital signs. What is the correct management?
A 5-year-old is brought in with progressive unsteadiness, then inability to walk, with absent deep tendon reflexes and normal mental status over the past 2 days. She is afebrile. Examination of the scalp reveals an engorged tick. What is the most appropriate next step?
An adult with a known wasp allergy is stung and develops hives, wheeze, and a blood pressure of 78/44. He takes metoprolol for hypertension. Which statement about management is most accurate?