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Tests and diagnosis
By Mayo Clinic staff
Your doctor may suspect a spider bite based on your history and your signs and symptoms, but a specific diagnosis is difficult to confirm. Confirmation requires:
- An eye witness to the bite
- Identification of the spider by an expert
- Exclusion of other possible causes
The black widow spider is a shiny black spider about a half-inch (12 to 13 millimeters or mm) long with a red hourglass (or two triangles) marking on the underside of its abdominal area.
The brown recluse spider is a brown, nondescript spider about a quarter-inch to three-quarters of an inch (6 to 19 mm) long. It has a dark violin shape on top of the leg attachment region but this can be hard to identify. Another characteristic of the brown recluse is that it has six eyes — a pair in front and a pair on both sides — rather than the usual eight eyes in two rows of four.
- Spider bites. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/print/sec21/ch325/ch325k.html. Accessed June 29, 2010.
- Vetter RS, et al. Approach to the patient with a suspected spider bite: An overview. http://www.uptodate.com/home/index.html. Accessed June 28, 2010.
- OSHA fact sheet: Black widow spider. Occupational Safety and Health Administration. U.S. Department of Labor. http://www.osha.gov/OshDoc/data_Hurricane_Facts/black_widow_spider.pdf. Accessed June 28, 2010.
- Vetter RS, et al. Bites of widow spiders. http://www.uptodate.com/home/index.html. Accessed June 28, 2010.
- Extension fact sheet: Black widow spider. The Ohio State University Extension. http://ohioline.osu.edu/hyg-fact/2000/2061A.html. Accessed June 28, 2010.
- OSHA fact sheet: Brown recluse spider. Occupational Safety and Health Administration. U.S. Department of Labor. http://www.osha.gov/OshDoc/data_Hurricane_Facts/brown_recluse_spider.pdf. Accessed June 28, 2010.
- Vetter RS, et al. Bites of recluse spiders. http://www.uptodate.com/home/index.html. Accessed June 28, 2010.
- Tetanus vaccine questions and answers. Immunization Action Coalition. http://www.vaccineinformation.org/tetanus/qandavax.asp. Accessed June 28, 2010.
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