Myth: Brown recluses bite everywhere

October 27, 2015
Rod Crawford

Myth: "I just know the dreaded Brown Recluse spider is in my area. Why? Because people have been bitten by them!"

Fact: Unless you live in the south-central USA (see map, below), where Loxosceles reclusa actually exists, human bite cases are reported from your area because of the incompetence of those reporting them, not because of actual spiders biting people. In the USA generally, there are hundreds of these cases reported each year, and at least 80% of them are false reports from areas where the spider supposedly responsible does not exist.

Distribution map of Brown recluse spider, Loxosceles reclusa

Brown recluse spider, Loxosceles reclusa. Real distribution in 2002; real bites do not occur outside green area!

"Brown recluse bite" has become medical shorthand for "this patient has a mysterious sore or lesion." In such areas as the Pacific coast states, it is safe to say that 100% of these reports are errors, and the vast majority (perhaps 95%) are not spider bite cases of any kind. It goes with the almost universally believed superstition, "if you didn't see what bit you, it was a spider." In reality, a variety of medical conditions (see this article) cause these mystery lesions, including lymphatic disorders, bacterial and fungal infections, and delayed-hypersensitivity allergic reactions — in addition to bites of ticks and other bloodsucking arthropods.

For a detailed analysis of the "bite" misdiagnosis problem in California, which has reached major proportions, see Rick Vetter's excellent web page: Myth of the Brown Recluse. A list of publications in medical journals on the epidemic of "brown recluse" misdiagnosis is available on request. Another brown recluse myth follows.

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Information on this web site is not a substitute for professional medical advice, and should not be used to diagnose or treat a medical or health condition. You should consult a physician as to any symptoms that may require diagnosis or treatment. Genuine spider bites can sometimes require medical attention, but beyond that, several medical conditions commonly mistaken for spider bite can be even more serious. If you have what appears to be a serious spider bite, please contact your health care provider or local emergency services. If you have the actual spider that bit someone, always save it for identification by a professional arachnologist.

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