Do they wash them??

I just came back in biz on an OZ flight Seoul to LAX.

On take off I started to smell a strong BO smell.
I thought, darn someone in here forgot to shower or change clothes.
It was very strong. I started to check around hoping to find the source with the thought I would change seats to get away from it..
Then I discovered it was from the OZ provided slippers in my cube, I had taken them out of the plastic prior to take off with the thought of using them later. OMG they smelled bad.
I gave them to the FA who offered another pair, which I declined.