I rinse out my helmet, foam, support, straps and all with cool water every now and again to get out the funk. Every few days if it's cool out, after every ride if I'm sweating, but that's just me. They get this nasty, salty-vinegar crap and pointy salt crystals, the straps get stiff and it's just gross...
Please realize any kind of damage to the helmet will reduce the rated safety factor, so periodically look for any cracks, pits, delamination, etc. and replace as necessary. Also, helmets have a shelf-life that expires after a certain length of time (like three years of use or something, check with Specialized for specifics) and replacement is suggested after that period.
If you ever do fall and hit your head the helmet is done, finito, used-up, whatever you want to say. Time to get a new one no matter now little damage you think you did to the helmet. Thank the now-useless lid for it's service and consider yourself lucky you avoided further injury. Here's to never having that happen though
Hopefully it will have an uneventful life doing nothing more than messing up your hair if you still have it, or giving you a weird tan if you're bald.