Several times a year, I’m sent pictures of what are identified as a series of recluse spider bites. The images begin relatively benign, with only a small wound, and then dramatically evolve into an ugly rotting lesion. They’re often accompanied by comments on how common, yet underappreciated, these dangerous spiders are.

Finding claims of recluse bites is easy. Finding documentation is difficult. The noted toxicologist Findley Russell, M.D. remarks that 8 out of 10 bites in one study were misdiagnosed.1   Sean Bush, M.D., an envenomation specialist at the Loma Linda University School of Medicine, and frequent lecturer for the Wilderness Medical Society, says that fewer than 100 recluse bites have been confirmed and documented in medical literature.

I’ve pursued the origin of these ugly images back through the e-mail trails.  No one has ever been able to verify a source.  Once I tracked them to a professional biologist, who embarrassingly admitted he might have forwarded an Internet myth.

Spider bites are a wonderful example of our tendency to react strongly and perhaps illogically to unknown or scary risks. Spiders, the lead characters in more than one horror flick, are symbols of venomous danger, of messy housekeeping or simple arachnophobia. They are easily, but perhaps incorrectly, blamed for wounds. This is an unfortunate character assassination. Few of the many spiders worldwide can actually injure people, and overall spiders are beneficial—like when they eat insects that infest our foods (flies), are vectors of disease (mosquitoes), or are just ugly and unwanted (cockroaches, earwigs).

The New England Journal of Medicine recently published an article that argues that brown recluse bites are rare, and rarely accompanied by the vivid wounds in Internet myth images.2  The first spider seen may be falsely accused of the deed, or misidentified, especially when it’s delivered to the emergency room as a squashed dark mess.

According to Rick Vetter of the Department of Entomology at the University of California-Riverside, brown recluse spiders are rarely confirmed in states where they are not resident (the central Midwest, Nebraska, south to Texas and eastward to southernmost Ohio and north-central Georgia).  Stories of brown recluse spiders outside areas where they are endemic are highly suspect.3

The hobo spider (Tegenari agrestis) allegedly causes a necrotic wound similar to that of the brown recluse spider, along with a characteristic persistent headache. But in its native European habitat, the hobo spider is not considered poisonous to humans.  Documented claims that hobo spider bites actually cause necrosis are also rare.

A venom detection test would help solve this question, but a reliable test is not available.

There are a number of folk remedies for spider bites, as well as web sites promising miracle cures.  In reality, nothing has proven much better for healing than time and good wound care.

Do people get bitten by brown recluse spiders and develop necrotic sores?  Yes, but it may be unlikely outside the spiders’ home range, and the bites are rare regardless. 

References:

1.   Russell FE, Gertsch WJ. For those who treat spider or suspected spider bites. Toxicon 1983;21:337-9.

2.   Swanson, D., and Vetter, R.  Bites of Brown Recluse Spiders and Suspected Necrotic Arachnidism. N Engl J Med 2005;352:700-7

3.   Vetter, Rick.  The Myth of the Brown Recluse.  Accessed August 5, 2005 at www.entomology.ucr.edu.