What Does a Brown Recluse Bite Do?

Often little at first. The Defense Centers for Public Health says the bite itself is generally painless and people are usually unaware of it until about eight hours later, when the site may become red, swollen and tender, and that only about 10 percent of bites progress to a gray or purple discoloration at the bite site. CDC's NIOSH says bites may cause a stinging sensation with localized pain and a small white blister, and that the venom can destroy skin tissue, causing a severe lesion that requires professional medical attention.

Most heal. The Defense Centers for Public Health says the majority of brown recluse bites heal completely within three weeks, but sometimes a lesion with a core of dead tissue develops and spreads or persists for weeks, and in some people the wound fails to heal and may require skin grafts. A July 2026 US military clinical guideline lists fever, weakness, vomiting, joint pain, rhabdomyolysis and hemolysis among signs of systemic loxoscelism, and says rare severe cases can result in kidney failure and death.

Location matters for diagnosis. The Defense Centers for Public Health says brown recluses are common indoors and outdoors only in their native range in parts of the South Central and Midwestern United States, and that bites attributed to them outside that range are highly unlikely and often misdiagnosed. In a 2000 article, entomologist Rick Vetter wrote that the distribution of recluse spiders indicates many diagnoses made on cases in the western United States are incorrect.

If you suspect a bite, the Defense Centers for Public Health advises applying ice to the bite site, elevating the affected area and seeking medical attention immediately. The military guideline says there is no antivenom available for recluse bites, and that early excision, injecting corticosteroids into the lesion and dapsone are not indicated.