The Xenaverse has had multiple episodes where Hercules, Iolaus, and Xena have been passed off as royalty. Now Gabrielle gets her first turn.
While sumac has multiple uses in medicine, food, and textiles, the "dye" that the street vendor would use the sumac for would be red, and therefore poisonous. Sumac can also be used for brown and black dyes. Sumac that is used for food would normally have the irritating fibers from the fruit which seem to be causing issues for Xena, though the sap is what can cause blindness.