Smiley says:
We are lucky it didn't crit...
Soooooo unbelievably lucky.
I, OOC, presume the fact that the coin was not dipped through the gross jar on the desk is the source of the rash. The items are probably enchanted and the wash is what removes it after purchase. Like the pin alarm on an expensive coat at the store. "Cleansing" the hourglass in the jar is probably her way of consenting to an item leaving the wagon after a purchase.
Briar, on the other hand (pun not intended), hasn't quite made that leap yet.