Demodex are microscopic, parasitic mites that live on the skin and hair follicles of the face including the eyelids and eyelashes. They feed on the oil content of sebaceous glands in the skin and the oil (meibum) in the meibomian glands of the eyes. While these mites are normally present in small numbers, an overgrowth or imbalance can be problematic and lead to a range of issues affecting the face and eyes. When their population grows excessively, they can cause conditions like chronic eyelid inflammation (blepharitis), exacerbation of ocular and facial rosacea and redness (telangiectasia) as well as worsening of dry eye disease.