Most spiders aren’t a danger to people because their venom is not strong enough to create any health risks. In general, spiders are shy and reclusive by nature, and they tend to stay hidden away from people. In fact, spiders usually only bite when they feel threatened, startled, or are being directly handled. While most spiders found living throughout the United States are harmless, some are considered dangerous because their venom is strong enough to cause significant health problems in humans.