Some spiders are a danger to people e.g. a sting from the well–known Black Widow spider (Latrodectus mactans)
can be deadly, but also the sting from the Brazilian Wandering spider (Phoneutria fera) can be fatal.
ATTENTION these are NOT bird spiders. The poison of a bird spider is almost negligible. This poison contains a high amount of amino acid and is only deadly for a warm–blooded animal like a mouse or a bird, when body mass exceeds 400 grams there is no further danger. When human beings get a sting from a bird spider this can be compared with a sting from a bee or wasp. Note that people who are allergic to a wasp's sting will react the same way to a sting from a bird spider.