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 eyewitness to the bite
- Identification of the spider by an expert
- Exclusion of other possible causes
Black widow identification
Some clues for identifying black widow spiders include:
- Shiny black body
- Large round abdomen
- Red hourglass on underside of abdominal area
- Central body about a half-inch (12 to 13 millimeters) long
- Entire body, including legs, can be more than an inch (2.5 centimeters) across
Brown recluse identification
Some clues for identifying brown recluse spiders include:
- Color ranges from yellowish tan to dark brown
- Dark violin shape on top of the leg attachment segment
- Six eyes — a pair in front and a pair on both sides — rather than the usual spider pattern of eight eyes in two rows of four
- Central body is a quarter-inch to three-quarters of an inch (6 to 19 mm) long
May 14, 2016
- Vetter RS, et al. Approach to the patient with a suspected spider bite: An overview. http://www.uptodate.com/home. Accessed March 8, 2016.
- Habif TP. Infestations and bites. In: Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Edinburgh, U.K.; New York, N.Y.: Mosby Elsevier; 2016. https://www.clinicalkey.com. Accessed March 8, 2016.
- Spider bites. Merck Manual Professional Version. http://www.merckmanuals.com/professional/SearchResults?query=spider+bites. Accessed March 8, 2016.
- Venomous spiders. National Institute for Occupational Safety and Health. http://www.cdc.gov/niosh/topics/spiders. Accessed March 8, 2016.
- Vetter RS, et al. Management of widow spider bites. http://www.uptodate.com/home. Accessed March 8, 2016.
- Vetter RS, et al. Bites of recluse spiders. http://www.uptodate.com/home. Accessed March 8, 2016.
- Brown recluse spider. Occupational Safety and Health Administration. http://www.osha.gov/OshDoc/data_Hurricane_Facts/brown_recluse_spider.pdf. Accessed March 8, 2016.
- Diaz JH, et al. Common spider bites. American Family Physician. 2007;75:869.
- Claypool DW (expert opinion). Mayo Clinic, Rochester, Minn. Nov. 24, 2014.
- Juckett G. Arthropod bites. American Family Physician. 2013;88:841.
- Black widow spider. Occupational Safety and Health Administration. http:www.osha.gov/OshDoc/data_Hurricane_Facts/black_widow_spider.pdf. Accessed March 23, 2016.