If it’s a strange sour smell, it may me created by bacteria that love a bit of humidity. The only way to get rid of the smell is to kill the bacteria once and for all. You can do it either by 1) using bleach (soak for 10-20 minutes in chlorine solution (the only occasion I ever use it), 2) airing the smelly items in sunshine so the UV rays can do the job. To avoid it in the future, be sure to dry them in plenty of air, and as quickly as possible. Freezing kills dust mites, but not these miserable creatures. Good luck! Kay