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The bad news is that some spiders do bite people, and these bites can be dangerous. The good news is that spider bites are actually quite rare events. A recent summary of reported spider bites in the United States between 1989 and 1993 included fewer than 5,000 incidents per year. Only a few of the bites of widow spiders were medically serious, but over 80% of recluse bites were considered serious. Only about 10% of other spider bites had serious consequences. These numbers seem small when compared to the over 800,000 dog bites that required stitches each year (source: Centers for Disease Control). During the study period, dog bites were responsible for 20 deaths per year, and auto-deer collisions were associated with 130 annual deaths. You might be surprised to learn that there were no spider-bite related fatalities during that four-year period.

Worried patients arrive at the hospital saying "I don’t know what bit me but it hurts so much it must have been a spider..." and unfortunately doctors are sometimes willing to accept this premise. In reality, many injuries that are reported as spider bites are actually caused by other small animals (fleas, lice, mosquitoes, biting flies, ant bites and stings, etc.). One national study of 600 cases of suspected spider bites established that approximately 80% were not actually caused by spiders.  A particularly famous headline story involved a group of injuries associated with orchard workers in Florida.  The workers' sores were first thought to be the result of spider bites, but they turned out to be secondary infections following spine punctures from working on the trees.

Spider bites are most serious when the victim is very young or aged.  Particularly sensitive persons of any age may also have an adverse reaction to animal bites. Many of us know someone who is very sensitive to bee or wasp stings. The bite of a normally harmless spider might be a serious problem for such a person. The venoms of spiders are the result of spiders’ adaptation to its predatory habits. The poison is generally most effective at killing their natural prey, usually an insect. Dangerous spider venoms usually act against the nervous system (neurotoxic) or the blood (hemotoxic), but humans are often unaffected by spider venom because of our large size and different physiology.

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There is no spider species anywhere that can properly be called "deadly." Obviously, a few people have died from spider venom, but I know of no species anywhere on earth capable of causing death in humans in as much as 10% of cases, even if untreated. If the person bitten obtains medical aid, death from genuine spider bite ("mystery bites" falsely blamed on spiders don't count) is almost unknown in North America and a decided rarity worldwide.

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