why does his underwear stink still?

Now don't get all grossed out here. My SO showers every day and changes his underwear after every shower like a normal person with good hygiene does. 
Well, his underwear stinks even after I wash them. Idk if it's just a man butt thing.. idk if man butts stink I've never smelled his butt so I don't know and holy hell I don't want to. And it's not like a shit smell either, it's like a dirty sock smell.  I pull them out of the dryer and everything else smells fresh and good while his underwear, wow. I cannot get the sweaty man butt smell out of them. 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors