More information discovered thanks to a pouch of Skittles Sours that The Glutenite is rather fond of (me too on occasion but just the purple and pink ones). I had no idea who made Skittles but a quick scan of the pack showed it was Wrigley's, the gum people. Turns out they also make the medicinal Lockets and Tunes.

Here's the gluten free / allergen list: