The notoriety of the brown recluse spider, Loxosceles reclusa, has resulted in many dermatological conditions being misdiagnosed as the bite of this arachnid. These misdiagnoses occur throughout North America and are of concern especially in American states and Canadian provinces where no brown recluse populations are known to exist.

About 40 medical conditions have been or could be misdiagnosed as recluse bites. A sampling of these misdiagnoses includes infections caused by Staphylococcus aureus, Bacillus anthracis, Borrelia burgdorferi, Sporothrix schenckii, the herpes zoster virus, and even lymphoproliferative conditions such as lymphomatoid papulosis.1 Because past medical reports of loxoscelism often did not adhere to the principles of evidence-based medicine, these erroneous reports artificially increased the list of signs associated with loxoscelism, decreasing diagnostic accuracy.