Hiya!
Me (DM): "Oh, uh...hold on... [rolls dice]. Gerdin? As you brush the crumbs of breakfast out of your beard you notice something on your finger tips. They are...bluish-purple; both hands".
Player: "What?! What is it? I wipe it off...?"
Me: "Nope. Won't come off. After a bit of vigorous rubbing they are starting to get both 'hot' and 'numb' at the same time".
Player: "Crap! Guys! I've been poisoned! Everyone check your fingers! See who else has been poisoned!"
Me: [rolls dice] "Terl, Valaria...you guys also have the same discolouration. Oddly, Nevven the thief DOESN'T have it..."
...hilarity ensues as Players loose their kittens, cast spells, drink potions and accuse Nevven of poisoning them.
...eventually...
Me: "Well, you all wake up the next day. The discolouration isn't gone, but it is lessened. Oh, and Gerdin? Yeah, you notice that the ladle you bought at that last town? It seems to be made of a wood that is excreting a purple sort of 'sap' when it warms up in the rabbit stew you are cooking. Nevven, you're not going to have any again are you? Considering you're a vegetarian, right?"?
^_^
Paul L. Ming