Yeah, I have a few Helly Hansen tops I wear for walking and they are pretty good at wicking and avoiding pong build up. I've also got a few pairs of socks which are made with silver coated thread, as it's antibacterial.
The ten days claim is a bit bogus though, as the person inside is going to reek after a few days if they haven't washed, so the state of the shirt is immaterial. (pun intended). If the wearer can wash, the shirt can be washed too.