Overview

Spider bites are usually harmless, and spiders don't usually bite unless threatened.

Spider bites can cause redness, pain and swelling, or you might not notice them at all. Many other bug bites and skin sores cause redness, pain and swelling. So unless you actually saw a spider bite you, it's difficult to be certain that your wound was caused by a spider.

Worldwide only a few species of spiders have fangs long enough to penetrate human skin and venom strong enough to hurt humans. Among these are widow spiders, with about 30 species, and recluse spiders, with more than 140 species worldwide.