Native range
Loxosceles reclusa is endemic to the south-central United States: Arkansas, Tennessee, Kentucky, Missouri, Oklahoma, Kansas, Louisiana, Mississippi, Alabama, Georgia, Indiana, Illinois, and parts of Texas. Cases reported outside this range are very rarely verified.
Clinical course
Initial bite is often painless. Within 2–8 hours, a sinking blue-gray macule with a surrounding pale halo and red rim may develop ('red, white, and blue' sign). Most lesions are self-limiting and heal without intervention.
Severe necrotic loxoscelism (<10% of verified cases) involves dermonecrosis over weeks. Systemic loxoscelism - hemolysis, renal failure - is uncommon and typically pediatric.
Treatment
Standard care is wound monitoring, tetanus prophylaxis, and analgesia. Routine surgical excision and dapsone are not recommended; they have not been shown to improve outcomes and may cause harm. Severe systemic cases require hospitalization.
References
- [1]Loxoscelism - Merck Manual Professional Version. Accessed June 2026.
Related in Bites and medical
- How to identify a spider biteMost lesions blamed on spiders are not spider bites.
- Black widow bite: symptoms and treatmentLatrodectism is the syndrome caused by Latrodectus envenomation.
- Spider bite vs. MRSA infectionThe most common misdiagnosis for a 'spider bite' is community-acquired MRSA.
- Are spider bites dangerous?For the average person in North America, spider bites are very rarely dangerous.
- Necrotic arachnidism: scope and overdiagnosisNecrotic skin lesions attributed to spiders are overwhelmingly caused by other agents.
- Antivenom for widow envenomationLatrodectus antivenom (Antivenin Latrodectus mactans, Merck) is effective at relieving systemic latrodectism but is reserved for severe or refractory cases due to the risk of acute hypersensitivity and serum sickness..