Doesn’t seem fair that such a tiny beast as a spider can cause lasting harm or even death to a big, vigorous human, does it? But then, venom and bacterial infections aren’t meant to be fair; they’re meant to stack the deck in favor of the tiny.
In North America, the two native spider species to watch out for are black (or brown) widows (various species of the genus Lactrodectus) and brown recluses (Loxosceles reclusa).
Brown recluse spider (aka Fiddlebacks)
This is what a brown recluse looks like. They’re sometimes called ‘fiddlebacks’ because of the darker violin shape on the thorax. Thanks Ohio State U. for the photo.
The brown recluse is actually not an aggressive spider. People generally get bitten only when they accidentally squish the spider, so if one’s running over your hand, flinging the hand about (screaming optional) works but swatting’s a bad idea. Brown recluses really are recluses, too: They don’t hang around where people usually are. Woodpiles and outbuildings are the most common places where people encounter them.
The bite of the recluse isn’t very painful, so people often don’t even realize they’ve been bitten until later when the venom makes itself known (often 12-24 hrs later, it’s suspected). Bites have been described as a kind of bullseye, with a red center with a lighter red ring around it. In about half of cases there will be some nausea, itching, feeling lousy, low-grade fever, and headache too, but these resolve on their own.
Venom kills tissue
The venom of the brown recluse causes considerable death of normal tissue cells near the bite site. More specifically, it tricks your immune system into killing your own tissues. (3)The problems with the wound keep developing for quite a while. The mild pain and redness of the first day develops some swelling, and about three days in you can tell there’s starting to be tissue death (dark purple at the edges, sinking in and getting black toward the center) even as the lesion continues to grow. (4)
After about a week the growth stops; and at 2-3 weeks in the dead tissue falls out, leaving pinkish granulation tissue around the inside of the pit where the dead stuff used to be. That pit takes a long time to heal. Fortunately, it’s not particularly prone to getting secondary infections. Bites to the face swell more, but fortunately don’t have as much tissue death.
In children
Occasionally (particularly in children) the venom will get into the bloodstream and cause generalized illness and a rupture of a lot of blood cells. The loss of blood cells leaves the person weak, pale, and tired; and can conceivably cause kidney failure and death. This is rare with the North American recluses though (sorry, Australians).
How do you treat these bites? Well, mostly take care of the wound to reduce the chance of secondary infection, apparently. There are antivenins, but a prepper’s not likely to have them; and they don’t work all that great anyway. (4,5) Symptom management such as antihistamines to reduce inflammation (think Benadryl or cortisones) and normal kinds of pain remedies if needed are generally put in the category of ‘might help and not likely to hurt’.
Black (and brown, and other kinds of) widows
The bad news about black widows is that they like to hang out in places like wood piles and fly-rich outdoor privies, and may be found inside in dark spots like closets too; and they have a reputation for being somewhat aggressive. Most bites occur when people hit their webs. (1) The infamous red hourglass shape on the abdomen is well known; but from my experience that can be hard to see on a scuttling beastie that likes the shadows, so I strongly resist contact with any black spider of that shape. Oh, what shape? This one:
Here’s a female black widow with her egg case. Thanks U of Mo. for the image.
The good news is that the danger from black widows is overstated. First, as Kipling would have it, “The female of the species is more deadly than the male.” Only female widows have long enough fangs to pierce human skin. Second, many bites are dry (no venom) risking bacterial infection as with any spider bite only. Third, venomous bites almost never kill humans: 0.5% was the highest estimate I found among several sources for the percentage of black widow bites that killed people; most estimates were much lower.
Still, an envenomed bite is not fun. It’s common to see two distinct puncture marks at the site, intense pain developing over the first ten minutes, and there may be sweating and goose pimple development near the site. The most common and troublesome symptom is intense and lasting (often for days) pain. Back and abdominal pain are most common from the North American species. The sweat patterns may be weird — such as just near the bite site, or on both legs but only below the knees. Sometimes general effects such as nausea and vomiting can occur.
What happens next?
The condition will resolve itself without treatment in the vast majority of cases, but some people report fatigue and muscle aches for weeks after. Giving muscle relaxants and pain control helps reduce symptoms. Some sources suggest that controlling the pain is important, since otherwise chronic pain might develop. Treating with calcium gluconate IVs used to be common but is no longer recommended. (And by ‘recommended’ I mean by the literature (2,4); I’m not a physician and don’t make medical recommendations.)
You may have noticed the ‘what can be done about it’ section of this article is pretty light. That’s not for lack of my looking; it’s because while lots of things have been tried, they’re seldom shown to be any better than normal supportive care. The good news is that none of the North American spiders is likely to kill a person. The problems usually do resolve completely just with that supportive care.
Spider bites without the venom
These two well-known venom injectors aren’t the only problem with spiders though, even if you live in an area where there aren’t any other known venomous species. Spider bites (venomous or not) are notorious for inoculating their victims with nasty bacteria. I’d always wash any bite carefully with soap, and watch it for signs of infection. It’s also likely, given the fact that we find new species of many-legged critters every time we look close, that there are more venomous species out there. Read here for an encounter between Salty and one of these beasts, and what it took to keep Salty walking among us:
PrepperMed 101: Hidden Danger – Spiders Can Hurt, Maim Or Even Worse
1) Venomous spiders. (2016) National Institute for Occupational Safety and Health. https://www.cdc.gov/niosh/topics/spiders/
2) Ryan, N. M., Buckley, N. A., & Graudins, A. (2017). Treatments for Latrodectism—A Systematic Review on Their Clinical Effectiveness. Toxins, 9(4), 148. http://doi.org/10.3390/toxins9040148
3) Patel, K. D., Modur, V., Zimmerman, G. A., Prescott, S. M., & McIntyre, T. M. (1994). The necrotic venom of the brown recluse spider induces dysregulated endothelial cell-dependent neutrophil activation. Differential induction of GM-CSF, IL-8, and E-selectin expression. Journal of Clinical Investigation, 94(2), 631–642.
4) Geoffrey K Isbister, Hui Wen Fan. (2011). Spider bite. The Lancet. Volume 378, Issue 9808,Pages 2039-2047. ISSN 0140-6736,
https://doi.org/10.1016/S0140-6736(10)62230-1.
5) Thomas Junghanss, & Mauro Bodio. (2006). Medically Important Venomous Animals: Biology, Prevention, First Aid, and Clinical Management. Clinical Infectious Diseases, 43(10), 1309-1317. Retrieved from http://www.jstor.org/stable/4485094
Great article. Having spent my entire life and career working in the shared environment with these creatures I can say that generally most spiders are not agressive even though the vast majority of spiders are venomous. Spider bites are never fun. Some species of spiders and a number of lepidopteran (butterflies and moth) catepillers also have uriticating hair. These are small hairs that break off and can cause a great deal of skin irritation. Some species of caterpillars uritacating hairs actually contain venom which makes them especially harmful. Better to do a little research and arm yourself with knowledge beforehand. During my career I assisted numerous medical doctors by identifying insects believed to be the cause of injury. The doctors were very competent, just not trained as entomologists and were not familiar with insects.
I read recently that the tissue damage from brown recluse bites is indistinguishable from other causes and Dr’s tend to diagnose it as a Brown Recluse bite even in areas of the country well outside that spider’s range. And give black spiders a break, Black Widow is the only common glossy black spider with a fat abdomen and very easy to id. And always look for a coarse and jumbled web.
We’ve been reading the same source perhaps; I saw that too — apparently (for those of you who haven’t read it) some of it is hobo spiders (in the Pacific northwest), some is tickborne disease (in the west). Apparently a lot of people never see the spider that bit them. This is common with widows, as they bite when squished, often while the larger victim is sleeping. That happened to my Mom in fact. Morning found her with muscle spasms and the spider flattened in her bed.