Brown Recluse Bites

How to Tell if You Were Bitten by the Dreaded Brown Recluse

Br-recluse-guy/Wikimedia Commons

The brown recluse spider is known to have a seriously venomous bite. It is responsible for a condition called loxoscelism, the only known cause of necrotic arachnidism (tissue death from a spider).

Pretty gnarly stuff, but not all skin boils and necrotic tissues are from brown recluse bites, or even spider bites at all. Since the chance of seeing a brown recluse in the act of biting is almost impossible (they are called recluses for a reason -- they don't like to be seen), figuring out if you were a victim of the dreaded brown recluse means doing a little detective work.

Where Did the Bite Occur (Geographically Speaking)?

Start by where you were when you got the bite. Brown recluse spiders don't live in the entire country, even though many people -- doctors included -- seem to think they do. They are found only in the southeast part of the US (see map). A few years ago, researchers from the Department of Entomology at the University of California, Riverside invited folks via the internet to send in spider specimens believed to be brown recluses.

Out of a total of 1,773 arachnids submitted -- remember, folks were only supposed to submit a spider if they thought it was a brown recluse -- there were 158 different species identified. There were spiders from 49 states sent in. Out of the 29 states where brown recluses are not common, only 2 brown recluse specimens were identified (lots of non-brown recluses were submitted, though).

This study found that if you get a "bite" (which actually could be any number of things) anywhere outside of where brown recluse spiders are known to live, the chances that it came from a brown recluse are essentially zero.

Got a bite in northern California or in Maine? There's no chance it's from a brown recluse, unless you just got back from Mississippi. The bottom line is, we can rule out the brown recluse as a cause of the bite if you aren't in the areas where brown recluses are known to live.

Was it a Brown Recluse?

So, assuming you're in brown recluse territory, it would be great if you saw the spider that bit you.

It would be even better if you still have it. An arachnologist (spider expert) could identify a brown recluse for you or your doctor. Your doctor, though, probably cannot.

Unless you're an arachnologist with a rather strong microscope, you can't identify a brown recluse. However, with a little knowledge, you might be able to identify whether or not the spider is at least in the recluse family. Here's what to look for:

  • Six eyes, set in 3 pairs called dyads. One dyad will be up front, the others on either side of the head. Most spiders have eight eyes.
  • Furry abdomen (the big part that looks like the spider's butt). It will have fine hairs and be all one color.
  • No spines on the legs and they're all one color.
  • Body (without the legs) can't be more than 3/8” long.

You may have heard brown recluses called violin spiders or fiddlebacks. These names refer to a common violin-shaped mark on the spider's back. It's not always obvious on brown recluses and it shows up on other species as well. So, look for the identifying information listed above instead of relying on the violin.

The problem is, more than likely you didn't even feel the bite happen. In most cases of loxoscelism, the bite is identified by symptoms several hours or days after the bite.

Symptoms of a Brown Recluse Bite

Most brown recluse bites either don't have any symptoms at all or have a little swelling and a red bump. Some brown recluse bites will develop a boil or a pimple and would be completely indistinguishable from an ingrown hair or a skin infection like staphylococcus or streptococcus.

Some of the worst brown recluse bites can lead to necrotic arachnidism, which looks like an open wound. Doctors often call those wounds ulcers. The term necrotic arachnidism literally means death by ally means death by spider and it refers to tissue death in the ulcer. Again, skin infections can lead to necrotic ulcers that look exactly the same.

The difference is that necrotic skin infections are much more dangerous and can be treated with antibiotics.

On the other hand, antibiotics don't do anything for brown recluse bites and there are very few confirmed deaths from loxoscelism. According to the University of California Integrated Pest Management Program, almost every death attributed to possible brown recluse bites happened in children and only about once per decade.

Treatment of a Brown Recluse Bite

Most brown recluse bites heal just fine without any medical intervention or first aid. If you see it happen or suspect that you were bitten, the recommended treatment is to use RICE (rest, ice, compression and elevation). Wrap the area of the bite with a compression bandage, use ice on it and elevate it.

If the bite develops into a boil or an ulcer, see a doctor. This isn't typically 911 worthy, but you'll want to get a physician to take a look. One thing a doctor might do is take a swab from the boil and culture it (test for bacteria). That way, if it can be treated with antibiotics, it will.

If you didn't see and feel the spider bite you, then there's really no way to know if it's a brown recluse bite or not. In that case, it's important to see a doctor for any boil or red, raised area that's getting worse -- especially if it feels hot and hard.


Swanson DL, Vetter RS. "Loxoscelism." Clin Dermatol. 2006 May-Jun;24(3):213-21. Review. PubMed PMID: 16714202.

Vetter, RS. "Arachnids submitted as suspected brown recluse spiders (Araneae: Sicariidae): Loxosceles spiders are virtually restricted to their known distributions but are perceived to exist throughout the United States." J Med Entomol. 2005 Jul;42(4):512-21. PubMed PMID: 16119538.

Vetter, RS. "Pest Notes: Brown Recluse and Other Recluse Spiders." UCIPM Online. Revised Jan 2008. Accessed 15 May 2012.

Vetter RS, Isbister GK. "Medical aspects of spider bites." Annu Rev Entomol. 2008;53:409-29. Review. PubMed PMID: 17877450.

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