The ones that are more material and less decoration could possibly be cleaned at home either by hand or in the washer. They should all come with washing or cleaning instructions from the manufacturer to guide the user on its care. A general rule would be that the more decorations of extra pieces the costume has, the less it can be cared for at home. You could take it to be cleaned at a dry cleaner, especially if it is one such as the Pirate costume with plenty of details in the design.