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Q: A friend was bitten by a spider. He developed a large swollen area on the leg, ran a fever off and on for three days, had aching in the shoulder, experienced pain in the leg (with difficulty walking at times). This bite had an effect on him for almost a week. What type of spider bite could have caused this reaction?
A: Most of the signs and symptoms we see associated with such bites are related to the spider's venom. This venom helps the spider in its hunt for insects, but is usually not toxic to humans (it most often causes only local tissue reactions). I cannot definitively identify which spider is the culprit in the scenario you have described. The non-specific findings may just be from the bite of any of a variety of brown spiders that usually cause mild swelling and pain, but are not dangerous.
In the United States there are only a few types of spiders that may raise concern -- most commonly the Black Widow (jet black with a red hourglass-shaped mark on its underside) and the Brown Recluse (violin-shaped marking on its head). The Black Widow tends to cause muscle spasms or cramps, but not much local tissue damage at the site of the bite. In comparison, the Brown Recluse tends to cause significant swelling, blistering, and bluish discoloration at the bite site.
With any bite, good local care is always recommended, including cleaning the area well, applying ice compresses to reduce the swelling and spread, and monitoring for any unusual complaints. Capturing the spider in a jar may be useful if you do seek medical care. Antivenin (a substance directed against the venom of a specific spider) is available for the Black Widow and Brown Recluse. However, antivenin can itself cause significant reactions, so judicious use is always recommended. If you have any concerns, call your physician or local poison center for specific advice.
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Henry Bernstein, M.D., is currently the associate chief of the Division of General Pediatrics and director of Primary Care at Children's Hospital, Boston. He also has an academic appointment at Harvard Medical School.