I'm tempted to try the dishwasher for mine.
Last year the Cat pee'd on my ski bag and got a bit of my helmet strap in the process.
: I hand washed it several times and cat spray-sprayed it and febreez'd it until I couldn't smell it anymore. BUT... the last few times I've skiied when I work up a sweat and the helmet gets warm I still get a slight whiff every now and then when I turn my head fast.
At least YOUR helmet only smells like head-funk.