Spider bites


Differential Diagnosis

Envenomations, bites and stings


  • Determine circumstances of bite to assess consistency with spider habitat and behavior
    • Indoors vs outdoors
    • Day vs night
    • Geographic location (recent travel)
  • Appearance of the spider if seen
  • Dead spiders can be preserved in 70% EtOH and later identified by arachnologists or entomologist

Clinically important spider genera by geographic region

  • North America
    • Loxosceles
    • Latrodectus
    • Tegenaria
  • South America
    • Loxosceles
    • Latrodectus
    • Phoneutria
  • Africa
    • Loxosceles
    • Latrodectus
  • Europe
    • Loxosceles
    • Latrodectus
  • Australia
    • Atrax
    • Hadronyche
    • Latrodectus
  • Asia
    • Latrodectus

Physical Exam

  • No pathognomonic signs proving lesion is a spider bite
  • Assess both bite site and for systemic signs
  • Bite Site
    • Location
      • Spider bites more common when clothing is tight against skin
    • Number of bites
      • Multiple bites suggest parasitic insect and not spider
    • Appearance of bite
      • Erythema, pallor, hemorrhage, induration, tenderness, paresthesia, vesicles
  • Systemic findings


See Also


  • Boyer LV, Binford GJ, Degan JA. Spider Bites. In Auerbach PS, Cushing TA, Harris NS. Auerbach’s Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017: 993-1016.