I've googled on how to remove it, but I don't get an adequate answer on where to find the ingredients. I'm in Chapter 2.
White Mirtle Petals: no problem.
Wolf's Aloe: Same as Wolf's Bane? Otherwise, no idea.
Green Mold: No clue.
Wolf's Aloe and Green Mold can both be bought from that witch in Lobinden. They're annoyingly pricey, though (over 100 orens each. Not too bad from an objective standpoint, but in comparison with other herbs it's kind of outrageous.)
I've also heard that the Wolf's Aloe is a rare drop from somewhere in the forest, but I've never found it.
Whoops, skimmed your post and didn't notice you were in Chapter 2. Sorry, but I'm not sure how to get it off on Iorveth's side. Since you can bring it up with Phillipa, though, I'd assume someone in Vergern sells the stuff you need.