205. Bites and Stings

Wasps, Bees, Ants / Hymenoptera

Bees/Apids and Wasps/Vespidae: honeybee/bumblebee sting when provoked, female stings only once since stinger embeds in skin and female eventually dies. Africanized honeybees/killer bees found in southern/warmer regions – stings not more toxic, but bees are more aggressive and hive can respond >10x number. Wasps/hornet/yellow jacket stings have more allergic response than bees – more volatile tempers. Hymenoptera venom contains histamine/melittin.

Sting: localized pain, erythema, edema, pruritis. Usually urticarial lesion. Can get systemic symptoms with multiple stings: resembles anaphylaxis with usually more nausea/vomiting/diarrhea. Can get headache, fever, drowsiness, involuntary muscle spasms, convulsions. Renal/hepatic failure can occur as well as DIC. CK elevations can cause rhabdo. Need to admit for observation is large amount of stings (>100). Anaphylaxis can occur within 15min-6hrs after sting. The shorter the interval, the higher chance of severity. Delayed reaction can occur 5-14 days after sting and produces serum-sickness reaction with fever, malaise, headache, urticaria, lymphadenopathy. Reports of encelopathy, neuritis, vasculitis, nephrosis with stings.

Treatment: remove bee stinger as soon as possible and wash area with soap/water. Systemic reaction: epinephrine 0.3-0.5mg IM 1:1000, 0.15mg for kids. Like anaphylaxis, consider given diphenhydramine/benadryl and ranitidine 50. Steroids can help limit urticaria/edema. Antivenoms have been study, but not available at this time.

Fire Ants/Solenopsis: similar reaction to bees/wasps. Fire ants can swarm and sting at the same time. Sting results in pupule in 6-24hrs which can lead to necrosis/scarring/secondary infection. Rhabdo and renal failure have been known to occur with large amount of stings.

Spiders / Araneae

Brown Recluse/Loxosceles: nocturnal, dry areas like basement, closets, woodpiles. Have pigmented, violin shaped pattern. Have characteristic eye pattern with only 6 eyes (most spiders have 8) with one anterior pair and two rows of 4. Venom: sphingomyelinase D. Bite is initially painless with mild erythema. Turns into mild/severe pain several hours after bite with localized erythema, pruritis, swelling. Hemorrhagic blister forms causing vasoconstriction-induced blanched skin. Day 3-4: hemorrhagic becomes ecchymotic (red, white, blue). Rarely causes systemic signs in the US, though can occur. Systemic effects include hemolysis usually in children and can occur 24-72 hrs after bite. Also can get nausea/vomiting/chills/arthralgias, thrombocytopenia, rhabdo, hemoglobinuria, renal failure. DIC can occur as well. Tx: if ulceration develops, surgical debridement will be delayed until clear margins usually at 2-3 weeks. Systemic symptoms following bite should require hospitalization. Dapsone (leukocyte inhibitor) has some recommendation, though still controversial. Can cause hemolysis and methemoglobinemia. No antivenom at this time, though studies are being done.

Hobo Spider/Tegenaria Agrestis: Pacific Northwest (where most hobos go?), similar to brown recluse; lives in moist dark areas. Similar presentation to brown recluse. Headache most common symptom. Tx: supportive care. No antivenom.

Black Widow/Latrodectus: black, but can also be brown/red as well. Orange/red hourglass marking. Usually in woodpiles, basements, garages, sheds. Bites occur usually between April/October. Highly potent venom: alpha-latrotoxin – releases neurotransmitters. Bite felt as pinprick, then increased local pain/cramping that spreads throughout extremity. Red macule that spreads into larger target lesion with blanched center and surrounding erythema. Muscle cramps, pain progressives with localized diaphoresis. Systemic signs: HTN, tachycardia. Tx: opiates/benzos are localized pain. IV calcium thought to help, though research says no. Latrodectus antivenom helps rapidly reduce symptoms and shortness illness. Administered IV. Derived from horse serum. Give slow administration diluted – relatively safe. Can be given 90 hours after bite if still having symptoms.

Armed Spider/Phoneutria: potent neurotoxic venom. From South America (Brazil area), hides in banana bunches. Usually no symptoms, though significant envenomation can produce severe pain, sympathetic (tachycardia, HTN) and parasympathetic (nausea/vomiting/diaphoresis/salivation) response. Tx: supportive care. Hold off on opiates due to can enhance effect on respirations.

armed spider

Funnel-Web Spider/Atrax/Hadronyche: construct cylindrical web. Found in Australia. Shiny black bodies. Neurotoxin venom. Causes local reaction with sweating/piloerection. Systemic symptoms: perioral paresthesias, parasympathetic response (salivation, bronchorrhea, nausea/vomiting). After bite, place compressive elastic bandage to length of limb and splint. Tx: Antivenom can be used with systemic symptoms: usually give 2 ampules q15 minutes; most patient require 4 vials.

Sac and Running Spiders/Cheiracanthium: house-dwelling, cytotoxic/neutotoxic venom. South African can produce skin necrosis. Symptoms usually of headache, malaise, dizziness, nauesa. Supportive care.

running spider

Tarantulas/Theraphosidae: hairy spiders that flick their hairs with two back legs. Hairs dont penetrate skin, though can get in conjunctiva/cornea.

Wolf Spider/Lycosa: small/medium sized; cytotoxic venom causing local pain, no systemic sympotoms.

Jumping Spiders/Salticidae: small, brightly colored. Localized pain only.

Daddy long-legs Spiders/Pholcidae: cellar/outbuilding spiders on Pacific coast/SW. ‘Toxic venom’ myth. No case reports of human envenomation.


Found in warmer southern US. Nocturnal. Bites similar to stings from bees/wasps. The Centruioides exilicauda/bark scorpion is only US scorpion to possess systemic toxicity.

Bark scorpion: can cause somatic and autonomic systems. Onset of pain and paresthesias in extremity that becomes generalized. Can affect CN and cause abnormal eye movements, fasciculations, blurred vision. Also restlessness, nausea, tachycardia, symptoms last for 24-48hrs.

Tx: supportive care, atropine can be used in USA for hypersalivation/respiratory distress, though its contraindicated outside US because it can flair up adrenergic effects. Antivenom available now – common in Arizona.

bark scorpion


Bites are often themselves. Its because they are disease vectors. Can transmit Lyme disease, Rocky Mountain Spotted Fever, ehrilichiosis, babesiosis, Colorado tick fever, tularemia, tickborne relapsing fever, tickborne encephalitis. Dermacentor andersoni/variabilis has neurotoxin that can cause tick paralysis with ascending flaccid paralysis with loss of DTRs, similiar to GBS except once tick removed, symptoms should rapidly improve. No sensory abnormalities and no abnormal protein level in CSF.


Mite larvae that attach and secrete digestive enzymes. Looks like bright red speck on skin. Intensely pruritic and have grouped papules/papulovesicles. Tx: oral antihistamines and topical steroids. Chiggers can be killed with permethrin and topical scabicides.

Other Bites

Mosquitos: redness, wheal, itching.

Flies: bloodsucking flies, varies in size. Some degree of pain/pruritis. Can produce allergic reaction. Can possibility cause myiasis (infestation of tissue with fly larvae) though fairly rare in the US. Recommend cold compresses, oral antihistamines, typical steroids.

Fleas/Siphonaptera: similair to lice and scabies mites. Make zigzag lines on legs/waist. Lesions usually have hemorrhagic appearing center surrounded by erythema and urticarial patches. Tx: local calamine application, cool soaks, oral/topical anthistamines, topical steroids.

Kissing Bugs/Bed Bugs/Hemiptera: look like apple seeds. usually painless. Erythematous papules, bullae and wheals. Tx: cool compresses, topical steriods, anthistamines. Bed bugs can survive up to 1 year without food. Washing at 60C, tumble drying at 40C is effective at all life stages. Resistance to large amount of pesticides. Use combination of insecticides if you are going to use them.

Caterpillars/Moths/Lepidoptera: Lepidopterism refers to contact with butterflies/moths/caterpillars. Caterpillars are harmless, localized dermatitis. The puss caterpillar/megalopyge opercularis can cause intense local burning pain with gridlike pattern of hemorrhagic papules within 2-3 hrs with regional adenopathy. Sometimes headache, fever, hypotension. Tx: Remove spines with adhesive tape.

Blister Beetles/Coleoptera: highly potent vesicant cantharidin which is expelled when body of beetle is crushed. Flick the beetle off. Can cause local inflammation leading to bullae formation and severe conjunctivitis is gets into eye. If ingested, can cause severe vomiting, hematemesis, abdominal pain, diarrhea along with dysuria, hematuria, oliguria and renal failure. Tx: supportive.


Q1. Patient was cleaning a basement when they felt a pinprick sensation on their foot. They attempted to look for the insect, but could not see it since it was too dark. They started to have cramping in their foot that then moved up their leg. They later started having generalized cramping. What type of insect were they stung/bite by?

A1. Black Widow spider. Wrong answers: Brown recluse, scorpion, Ixodes tick, tarantula, daddy long-legs.

Q2. Which type of spider has an antivenom available in the US?

A2. Black Widow. Wrong Answers: Brown recluse, Hobo spider, daddy long-legs, tarantula.

Q3. Why are africanized or killer bees more ‘deadly’ than regular bees?

A3. More aggressive; hives attack in larger size than regular bees. Wrong answers: Larger stingers, more toxic stings, stinger includes a venom, etc.


Tintinalli, Seventh Edition, Chapter 205: Bites and Stings

Bed Bug Infestation Clinical Review, Celine Bernardeschi, BMJ, Jan 2013

CrashingPatient.com, Scott Weingart, Venomous Animal Injuries

205. Bites and Stings

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