DH & I both use shampoo in the shower to clean our helmets. I've had really good luck w/ Nature's Miracle for bike clothes funk. A glug in the washer seems to cut the stink. It's an enzyme cleaner sold in pet stores for pet "messes." It works on anything organic. Besides bike clothes, I've used it on milk spilled in mini-van in August in Texas, vomit, dog/cat messes, & my son's football clothes left in a locker for a week with a damp towel. So I think it'll work for helmets too.