The area becomes dusky and a shallow open sore forms as the skin around the bite dies (necrosis).

[1][a] While there is no known therapy effective for loxoscelism, there has been research on antibiotics, surgical timing, hyperbaric oxygen, potential antivenoms and vaccines.

[1] The toxin dissolves the structural components of the cell membrane generating ring forms that perhaps act as a trigger for cellular self-destruction.

[9] The mnemonic "NOT RECLUSE" has been suggested as a tool to help professionals more objectively exclude skin lesions that were suspected to be loxosceles.

[10] Numerous (should be solitary), Occurrence (wrong geography), Timing (wrong season), Red Center (center should be black), Elevated (should be shallow depression), Chronic, Large (more than 10 cm), Ulcerates too quickly (less than a week), Swollen, Exudative (there should be no pus, it should be dry)[11] Systemic loxocelism, a rare but severe illness caused by a brown recluse bite, can be diagnosed through urinalysis.

There are several anti-venoms commercially available in Brazil, which have been shown to be effective in controlling the spread of necrosis in rabbits.

Most victims do not seek medical attention within the first twelve hours of being bitten, and these anti-venoms are largely ineffective after this point.

[citation needed] In cases where a large dermonecrotic lesion has developed, the dead tissue can be surgically removed.

The range of the brown recluse spider extends from southeastern Nebraska to southernmost Ohio and south into Georgia and most of Texas.

[16] There have been documented cases of homes having very large populations of brown recluse spiders for many years without any of the human inhabitants being bitten.

[citation needed] Loxosceles laeta, commonly known as the Chilean recluse spider, is widely distributed in South and Central America.

It can be transported by people, and populations in solitary buildings are noted in North America, Finland, and Australia.

[19] The white-tailed spider, found principally in Australia, was formerly blamed for a series of illnesses including necrotic arachnidism.

[20] Cheiracanthium inclusum, also known as the black-footed yellow sac spider, has been implicated in necrotic skin lesions.

[citation needed] Many necrotic lesions in the northwestern United States have been attributed to spider bite.

in antivenom studies in Brazil in the 1920s first focused on Lycosa species as causes for illness and widespread necrotic lesions.