I have read about a lot of people having problems with stincky helmets. I have never had that issue. For it to be smelly, it means you have bacteria in there which is either due to a dirty head or dirt inside you helmet which mixes with your head. Either way you guys really need to be more careful!
I have a charles owen and I would not put in the dishwasher. Cleaning instructions came with the helmet if you have them.
I looked up the instructions for you: http://www.charlesowen.co.uk/en/products/carehelp.php