I saw him parodied on Saturday Night Live several weeks ago. They implied that he does not bathe regularily and doesn't wash his clothes just buys new ones when he grows out of them. Was this true? I didn't think so but then these skits are sometimes based on truth. He doesn't look like the cleanest person in the world, at the very least.
Even back in the 1950s, Howard Hughes didn't dryclean his shirts. He would wear them until they became too unclean and then put on a new shirt.
He also conveniently didn't carry a wallet (giving people around him the "honor" of buying Howard Hughes a meal).