Can anyone please explain to me why I'm still getting the message "you have been poisoned" whenever I fight frostbite spiders or the like (anything that uses poison)??

I read on the wiki that there is a hard cap on poison resistance at 85% so it is technically impossible to be "immune" to poison, so what? Does the vampirism resistance really only give you an effective 85% resistance??
Disease immunity seems to be working just fine btw....