Spider Bites
Written by Jeffrey Davis on June 14, 2011, 11:23 p.m.
Spider Bites

Bites usually present as a solitary lesion they can be painful or painless, there can be death of the tissue due to envenomation (particularly with recluse spiders) or if the venom enters the bloodstream the effects can be widespread (systemic).
Here’s the rub when it comes to diagnosing spider bites according to the medical literature:
A presumptive diagnosis of a spider bite is most often based on the history and clinical presentation. However, the diagnosis of a spider bite can be considered definitive ONLY if both of the criteria below are fulfilled:
- A spider was observed inflicting the bite.
- The spider was recovered, collected, and properly identified by an expert entomologist.
There’s a common expression, when you hear hoof beats look for horses rather than zebras. So as physicians we look for other reasons.
- Infections: MRSA (a common staph infection) very often starts with a single red, swollen, tender lesion. Lyme’s disease (spread by ticks) also have a characteristic target-like lesion. Herpes can also present with a single lesion.
- Other bites and stings: Ants, fleas, bedbugs, ticks, mites, mosquitoes, and biting flies can also sting or bite humans.
- Other common rashes: Poison oak, ivy and other plants can present with single lesions (although linear spread of lesions is more common.)
