A household appliance for treating at least one item according to at least one cycle of operation includes a treating chemistry dispenser receiving a unit dose container and having a door moveable between an opened position and a closed position, a piercing mechanism located proximate to the treating chemistry dispenser and having a piercer that is moveable between a non-piercing position and a piercing position where the piercer is moved to perforate a unit dose container received within the treating chemistry dispenser.