Just also to be on the safe side - do you have any small pets or animals in your home? That to me sounds like a mite. Mites can do a lot of harm to pocket pets (living animals) and possibly even kill them if not treated properly. If you do have small animals look in their arm pit area to see if you can catch more running around. I don't know if larger animals like cats and dogs get mites of such small size, but if you have them possibly check them too?
:c Not trying to freak you out, I had hermit crabs with mites before in the past and it was sad and icky. Just want to make sure your pets (if any) are okay and healthy!
-Purn