How do you know a spider has poison?

Answer 1

to my understanding, most if not all Spiders are venomous but the vast majority of them are not dangerous to humans, although they will most likely cause some pain. most household spiders are completely harmless. the ones you need to watch out for depend on where it is you live but assuming you live in the USA the first two that come to mind in terms of what you might find in your home are the black widow and the brown recluse, both of which are potentially deadly if the bite is not treated soon enough. if you want to know what they look like just do a Google image search.