How do you tell a dangerous spider bite from a harmless one, and when should you actually go to the hospital?

With a scary spider bite story trending, what are the actual warning signs that a spider bite needs medical attention versus one you can just treat at home?

Most spider bites, even from species considered "dangerous," cause only mild, localized symptoms — redness, swelling, and itching that resolve on their own with basic care (cleaning the area, a cold compress, over-the-counter pain relief). The warning signs that warrant medical attention are: a wound that keeps expanding, turns dark or develops a blister/open sore in the days after the bite (a possible sign of a brown recluse bite, which can cause tissue damage), significant pain that spreads beyond the bite site, muscle cramping or rigidity (a hallmark of black widow bites, which affect the nervous system), fever, chills, nausea, or difficulty breathing. If you can safely capture the spider (even a photo) without risking another bite, it can help doctors identify the species and treat accordingly, though it's not essential — treatment is based on symptoms either way. Anyone with a compromised immune system, blood clotting conditions, or other significant preexisting health issues should have a lower threshold for seeking care after any spider bite, since — as the recent Cheney Lake, Kansas case showed — bites that would be minor for most people can become serious complications for those with certain underlying conditions.