How Dangerous is the Bite of a Recluse Spider?

The composition of Recluse Spider Venom, and its Effects on Mammalian Tissue

All recluse spiders (members of the family Sicariidae, which in North America is represented by the single genus Loxosceles) are known to pose, under certain conditions, a danger to human health. In susceptible individuals, their venom produces severe cases of dermonecrosis and, rarely, systemic pathological conditions. In other individuals the effect of recluse spider bites is mild or of no consequence.

In North America, most cases of recluse spider envenomation, when the spider can be captured and identified, are found to involve the brown recluse (Loxosceles reclusa). This species is said to possess a particularly potent venom, while the venom of other Loxosceles species native to North America, save perhaps Loxosceles laeta, are thought to be less dangerous.

Despite considerable bad press that suggests otherwise, the bite of the brown recluse appears, more often than not, to be of little or no danger to the person bitten. It is common for persons living in homes infested with this spider to be bitten by them on a regular basis without suffering any ill effects. On the other hand, it is common for physicians to diagnose a necrotic lesion of unknown etiology as a "brown recluse spider bite" even though (1) the patient is not able to attribute the condition to the bite of a spider,  and (2) the brown recluse is either only rarely found or not known to inhabit that locale. Often, such lesions are caused by biological agents, such as the bacteria Staphylococcus aureus, the most common cause of staph infections. Approximately 20% of humans surveyed are found to be long-term carriers of this bacteria. Many of such carriers suffer no outward effects, while others exhibit low-grade staph infections such as pimples and the like, and some suffer more serious infections, including necrotic lesions.