Spiders are arachnids and closely related to other arachnids like ticks, mites and scorpions. They have two body regions, no antennae and eight legs. Spiders help to kill pests both inside and outside of buildings, and are beneficial. There are only a few spiders whose bite requires medical attention, such as the western or black widow spider, brown recluse spider, yellow sac spider and hobo spider.
Spiders are often more of a perceived pest than a clinical risk. Spiders generally will not bite unless accidentally trapped against the skin or grabbed. Some species actively guard their egg sacs or young. Many spider species are too weak to puncture human skin. When envenomation does occur, mild reactions may include slight swelling, inflammation, burning or itching sensations lasting a few hours.
Spiders are often implicated by medical professionals when patients present skin lesions. However, a US study showed that of 600 cases of suspected spider bites, approximately 80% were not caused by spiders. Very few fatalities occur, usually fewer than three annually.