Demodex folliculorum is a microscopic mite that can only survive on the skin of people. Most people have D. folliculorum on their skin. Usually, the mites do not cause any harm, and are therefore considered an example of commensalism rather than parasitism. If D. folliculorum does cause disease, this is known as demodicosis.
The treatment options listed on Medscape include:
Various treatments have been used to control Demodex mites. Most treatments involve spreading an ointment at the base of the eyelashes at night to trap mites as they emerge from their burrow and/or move from one follicle to another. A tea tree oil product (Cliradex) can be used. Terpinen-4-ol is the most active component of tea tree oil.
Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of this clinical setting.
Erythromycin ophthalmic (Ilotycin)
Belongs to the macrolide group of antibiotics. Basic and readily forms a salt when combined with an acid. Inhibits protein synthesis without affecting nucleic acid synthesis. Used for the treatment of ocular infections involving the lids, conjunctiva, and/or cornea caused by organisms susceptible to it.
That's all fine. But "Used for the treatment … caused by organisms susceptible to it" seems strange. Demodex mites are not bacteria. How are they susceptible to antibiotics?
This seems not to be used for prevention or treatment of secondary/bacterial infections:
Next, apply an antibiotic/steroid ointment to help keep the mites from moving and possibly suffocate them.
Demodex infestation requires immediate, aggressive treatment by doctor, patient, Healio, Primary Care Optometry News, 2011
How does this work?