Somewhat bemused at Percy's reaction, Sarah adopted her most patient tone. "Well, you're partially right. Scurvy-grass is a typical remedy, and lovage is used to improve the taste of many tonics, but," she paused, the irony of knowing more than Percy about something sinking in, "not in tonics containing scurvy-grass. Those two ingredients taken together would have you two-thirds of the way to a Confusing and Befuddlement Draught."
She moved towards the table again, where the prescription pad lay, and picked it up. "You'll know, I would imagine, that a fully brewed Confusing and Befuddlement Draught can make a person hot-headed and reckless." She paused to find a quill. "Well, combining two of the ingredients with the rest of the ingredients for a tonic simply enhances whatever is going on in your head, physically, anyway. So, it doesn't cause headaches, but it can make them stronger and longer-lasting."
Sarah quickly scribbled a prescription for the Draught of Peace on the top sheet of the pad and held it out to Percy. "So, either you have a sloppy apothecary, or you might have tried two different tonics with these ingredients too closely together...either way, this should help you. One dose, once a week, for the next month, and it should have flushed all the tonic remnants out of your system."