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Emergency: requires immediate attention
Recluse spider envenomation in Child
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Recluse spider envenomation in Child

Contributors: Robert Norris MD, Joanne Feldman MD, MS, Susan Burgin MD
Other Resources UpToDate PubMed


The brown spiders, Loxosceles species, are found in temperate and tropical latitudes around the world. They live indoors and outdoors in dark areas where they build messy webs. Recluse spiders are most abundant and active at night during the warm months, are non-aggressive, reclusive, and prefer to retreat when threatened. Loxosceles spiders are typically brown in color, measure 2-3 cm from leg to leg, and have 6 eyes arranged in 3 pairs (most spiders have 4 pairs). The brown recluse spider Loxosceles reclusa has a characteristic dark, violin-shaped spot on the dorsal aspect of the cephalothorax.

Envenomation by Loxosceles species (loxoscelism) can result in dermonecrosis and, less commonly, a potentially fatal systemic illness that includes hemolysis and rhabdomyolysis, with subsequent renal failure. Loxosceles venom contains cytotoxic, proteolytic, coagulopathic, and hemolytic components. The primary toxic component is sphingomyelinase D, which is largely responsible for necrosis and hemolysis. Hyaluronidase causes the characteristic gravitational spread of the lesion.

The North American brown recluse (L. reclusa) is the most common Loxosceles species responsible for human injury. The Chilean recluse venom (Loxosceles laeta) is the most toxic and poses a serious public health threat in South America. Envenomation causes several deaths per year in South America. Death is extremely rare in the United States.

Brown spider bites typically occur during dressing or sleeping when spiders become trapped in clothing or bed linens. The bite can produce a sharp, stinging sensation, although frequently the victim is unaware of having been bitten. The spider is rarely seen. Characteristic of Loxosceles envenomation, severe burning pain and pruritus develop at the bite site within 2-6 hours. Over time, the wound typically develops an erythematous halo surrounding a central hemorrhagic vesicle. Occasionally, the central vesicle will be surrounded by an area of ecchymosis, surrounded by a ring of pallor and an outer ring of redness. By day 3 or 4, the hemorrhagic vesicle becomes necrotic, and an eschar forms. After 2-5 weeks, the eschar sloughs, leaving an ulcer that often heals by secondary intention, though some may require skin grafting. In severe cases, there can be progressive tissue necrosis that is particularly severe in fatty regions such as the buttocks or thighs.

The incidence of systemic involvement varies by species and geography and is more common in children. Loxosceles reclusa of North America rarely causes systemic symptoms, while systemic involvement is not uncommon with the South American L. laeta. As early as 24 hours after envenomation, fever, arthralgias, nausea, vomiting, diarrhea, rash, myalgias, and headache can develop. With more severe systemic illness, hemolysis is the predominant feature. Thrombocytopenia, disseminated intravascular coagulopathy, proteinuria, renal failure, and death have been reported.


T63.331A – Toxic effect of venom of brown recluse spider, accidental, initial encounter

40119006 – Poisoning due to brown recluse spider venom

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Differential Diagnosis & Pitfalls

  • CA-MRSA skin infection (presenting as Skin bacterial abscess or Furunculosis) are often mistaken for spider bites. Have a very high suspicion for CA-MRSA and discount the patient history of a spider bite if there is any clinical suspicion of CA-MRSA.
  • Caterpillar dermatitis
  • Cellulitis
  • Centipede envenomation
  • Allergic contact dermatitis / Allergic contact dermatitis
  • Ecthyma
  • Factitial ulcer
  • Hymenoptera stings (eg, Honeybee sting, Wasp or yellow jacket sting)
  • Lyme disease
  • Medication-induced drug reactions such as Stevens-Johnson syndrome and Toxic epidermal necrolysis
  • Warfarin necrosis
  • Arthropod bite or sting (eg, biting flies, assassin bugs, kissing bugs, or Scorpion sting)
  • Other Spider bite (eg, Hobo spider envenomation, sac spiders, or Chiracanthium species)
  • Chemical burn
  • Leukocytoclastic vasculitis
  • Ecthyma gangrenosum
  • Factitial ulcer
  • Lymphomatoid papulosis
  • Primary syphilis
  • Acute febrile neutrophilic dermatosis
  • Necrotizing fasciitis
  • Pyoderma gangrenosum
  • Skin infections caused by Cutaneous anthrax, Streptococcus, Sporotrichosis, Herpes zoster (shingles), and Disseminated herpes simplex virus with immunosuppression
  • Tetanus
  • Tularemia
  • Ergotism
  • Neurogenic ulcer
Pitfall: Doctors and the public frequently diagnose a variety of lesions as "brown recluse bites" despite the fact that the brown recluse is most commonly found in Midwestern and southern states of the United States.

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Last Reviewed:05/14/2017
Last Updated:06/13/2018
Copyright © 2024 VisualDx®. All rights reserved.
Emergency: requires immediate attention
Recluse spider envenomation in Child
A medical illustration showing key findings of Recluse spider envenomation (Initial Findings)
Clinical image of Recluse spider envenomation - imageId=1866747. Click to open in gallery.  caption: 'A giant erythematous plaque with overlying crusting and similar surrounding papules on the arm.'
A giant erythematous plaque with overlying crusting and similar surrounding papules on the arm.
Copyright © 2024 VisualDx®. All rights reserved.