Puzzle Pharmacy - The source of my headache

Ironically most people go to a pharmacy to relieve a headache, but if you are the pharmacist, pounding with a mortar and pestle all day will certainly give you one. Imagine trying to mash up those twigs? Then the headache of hearing people complain of how nasty the stuff tastes, or how they went blind with the mixture. All day long it's, wah wah, I can't taste anything... My vision, where did everyone go? I'm sicker now than when I was before I came here. Good thing you know how to make a good cure for headaches.