Bites of recluse spiders
- Richard S Vetter, MS
Richard S Vetter, MS
- Department of Entomology
- University of California, Riverside
- David L Swanson, MD
David L Swanson, MD
- Associate Professor of Dermatology
- Mayo Clinic
- Section Editors
- Daniel F Danzl, MD
Daniel F Danzl, MD
- Section Editor — Environmental Emergencies
- Professor of Emergency Medicine
- University of Louisville School of Medicine
- Stephen J Traub, MD
Stephen J Traub, MD
- Section Editor — Toxicology
- Associate Professor of Emergency Medicine
- Mayo Medical School
- Deputy Editor
- James F Wiley, II, MD, MPH
James F Wiley, II, MD, MPH
- Senior Deputy Editor — UpToDate
- Deputy Editor — Adult and Pediatric Emergency Medicine
- Deputy Editor — Primary Care Sports Medicine (Adolescents and Adults)
- Clinical Professor of Pediatrics and Emergency Medicine/Traumatology
- University of Connecticut School of Medicine
The entomology of recluse spiders (Genus Loxosceles) and the clinical manifestations, diagnosis, differential diagnosis, and management of their bites will be reviewed here.
An overview of spider bites and the management of bites of other spiders are discussed separately. (See "Approach to the patient with a suspected spider bite: An overview".)
ENTOMOLOGY OF RECLUSE SPIDERS
Spiders of the genus Loxosceles are known colloquially as recluse spiders, violin spiders, fiddleback spiders, and in South America, by the nonspecific name "brown spiders." These terms are used when describing multiple Loxosceles species as a group. When the common name "brown recluse spider" is used here, it refers only to the one species, L. reclusa, which is widespread and commonly found in homes in the indigenous Central Midwestern United States.
Loxosceles spiders have gained notoriety in the medical literature and lay press because their bites sometimes become necrotic [1,2]. However, this is a relatively uncommon sequela, and is largely limited to areas of the United States where these spiders are endemic (figure 1). Outside of these regions, the vast majority of necrotic skin lesions are caused by other disorders [3-6]. (See 'Differential diagnosis' below.)
Appearance and identification — Recluse spiders are rather nondescript brown spiders (picture 1 and picture 2). The most accurate method of identifying a recluse spider involves counting the eyes. Most spiders have eight eyes in two rows of four. In contrast, recluse spiders have six eyes, with a pair in front, a pair on both sides, and a gap between the pairs (picture 3). With the naked eye or low magnification, the eye pairs (dyads) may appear as individual eyespots.
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- ENTOMOLOGY OF RECLUSE SPIDERS
- Appearance and identification
- Geographic location
- - Habitat
- CLINICAL MANIFESTATIONS OF BITES
- Venom properties
- Clinical history
- Findings following bites
- - Local effects
- - Systemic findings
- Life-threatening effects
- Further evaluation
- DIFFERENTIAL DIAGNOSIS
- Solitary ulcerated lesion
- - Infections
- - Vascular disease
- - Pyoderma gangrenosum
- - Vasculitis
- - Pustular dermatosis of the dorsal hand
- Systemic reactions
- Patients with local effects
- - Wound care and general measures
- - Dermal necrosis
- Patients with systemic toxicity
- - Acute hemolytic anemia
- - Rhabdomyolysis
- - Disseminated intravascular coagulopathy
- South American recluse spider bites
- PEDIATRIC CONSIDERATIONS
- DISCHARGE INSTRUCTIONS AND AFTER CARE
- ADDITIONAL RESOURCES
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS