Just found out I'm allergic to dust mites!  The main species are cosmopolitan pyroglphids but I call them House dust mites. 
I've always heard of them but don't know much about them.
they are so gross - they feed on skin flakes from people and pets, and sometimes mold. 
That does sound nasty, can people see them? Or are they microscopic?
, due to their very small size and translucent bodies, are barely visible to the unaided eye. A typical house dust mite measures in length. For accurate identification, one needs at least 10× magnification. The body of the house dust mite has a striated cuticle.
Biology Diet.
They feed on skin flakes from animals, including humans, and on some mold. "Dermatophagoides farinae" fungal food choices in 16 tested species commonly found in homes was observed "in vitro" to be "Alternaria alternata", "
of birds and animals. These mites are largely parasitic and consume blood, skin and keratin. Dust mites, which feed mostly on dead skin and hair shed from humans instead of consuming them from the organism directly, evolved from these parasitic ancestors.
Parasitic mites sometimes infest insects. "Varroa destructor" attaches to the body of honey bees, and "Acarapis woodi" (family Tarsonemidae) lives in their tracheae. Hundreds of species are associated with other bees, mostly poorly described. They attach to bees in a variety