I would take it serious. Slayer guitarist Jeff Hanneman dies of liver failure after spider bite - Arts & Entertainment - CBC News
Then there is this news:
According to the American Association of Poison Control Centers, only two people died from spider bites between 2001 and 2005. Both were believed to be caused by brown recluse spiders.
Not bad unless you are one of the 2.
Whatever your hand finds to do, do it with your might; for there is no work, nor device, nor knowledge, nor wisdom, in the grave, where you go.