The brown recluse spider may be uniquely attractive to spider-watchers, but if you're a dog parent, you'll want to be extra careful when it comes to this arachnid. A brown recluse bite on a dog tends to be painful and possibly dangerous. What's more, clinical signs of a brown recluse spider bite in dogs can be hard to identify — particularly, early on. Let's take a closer look at what these spiders do and how to help your dog if they've been bitten.
Identifying a Brown Recluse Spider
As its common name suggests, this spider is brown in color and generally reclusive. As noted by the Merck Veterinary Manual, the distinctive "violin-shaped marking" on this spider's cephalothorax (upper body) is one of few features that makes this spider identifiable. However, this reclusive spider typically doesn't hang around long enough for a positive ID.

The brown recluse tends to avoid humans and dogs, whenever possible, but will bite when disturbed. Measuring 1 to 1.8 centimeters in length from the tip of its tiny head to the end of its bulbous abdomen, with longer legs measuring 2 to 3 centimeters, this creature's bite is notoriously destructive to the skin of both humans and dogs. The poison this spider wields is considered a formidable venom. While it can be merely painful at the outset, it can lead to tissue death and ulceration, sometimes in an area several times larger than the spider itself.
The brown recluse spider can be found in a wide geographic range. It lives in the Midwest section of the U.S., from Colorado and New Mexico in the west to Northern Georgia in the east. It also lives throughout southern portions of the U.S. and up the Mississippi into Wisconsin.
Recognizing the Clinical Signs of a Brown Recluse Bite
While the bite is somewhat distinctive, clinical signs of a brown recluse spider bite in dogs may initially be mistaken for a wide variety of other bites and stings. Your dog may also show no clinical signs that they were bitten or display non-specific signs, such as limping or shaking.
Clinical signs of a brown recluse spider bite in dogs include the following:
- Mottled and reddened skin in the form of a "bullseye" lesion
- Deep ulcers on the skin
Less common signs of a brown recluse bite on a dog include systemic effects from the venom, including:
- Fever
- Shaking
- Rashes
- Lethargy
- Weakness
- Nausea
Some dogs may also experience damage to red blood cells, which can lead to anemia and hematuria (blood in the urine). This typically occurs within the first 24 hours after a brown recluse bite on a dog. While rare, the venom of a brown recluse can enter a dog's bloodstream and lead to renal failure, gangrene, blood clotting problems and dangerously severe destruction of red blood cells.
