Brown Recluse Spider Bite: Identification, Progression & Medical Management

Loxosceles reclusa bites are frequently misdiagnosed. True envenomation follows a characteristic but variable course that clinicians should recognize.

Bite Evolution Timeline

Time	Findings
0–2 hrs	Often painless; mild stinging possible; minimal erythema
2–8 hrs	Erythema, edema, vesicle formation; "target lesion" (central blister, pallor, outer erythema)
24–72 hrs	Vesicle → hemorrhagic bulla → necrosis (eschar); pain intensifies
3–14 days	Eschar sloughs → ulcer (cm-scale); granulation begins
Weeks–months	Healing with scar; some require grafting

Systemic Loxoscelism — Rare but Severe

• Fever, chills, nausea, myalgias, hemolysis (especially in children or those with G6PD deficiency)
• DIC, renal failure, rhabdomyolysis, death (extremely rare)

Differential Diagnosis (Common Mimics)

• MRSA abscess (most common misdiagnosis)
• Streptococcal cellulitis
• Herpes zoster/simplex
• Vasculitis, pyoderma gangrenosum
• Diabetic ulcer, calciphylaxis

Management

1. Supportive: RICE (rest, ice, compression, elevation), analgesia, tetanus update.
2. Antibiotics: Only if secondary infection is present (cover MRSA).
3. Dapsone: Controversial; limited evidence; G6PD screening required before use.
4. Antivenom: Not commercially available in the US.
5. Surgery: Delayed debridement/grafting after demarcation (weeks later).

Critical Action

Seek medical evaluation for any necrotic-appearing lesion. Bring the spider if captured safely. Most "spider bites" are actually skin infections requiring antibiotics—not dapsone.