Demodex mites are acquired shortly after birth and are considered to be normal skin fauna that increase in number as people age. Almost everyone has a certain degree of the Demodex mite on his or her skin.[10] Heavy infestations of Demodex can arrive in adolescence, and could last up to middle age. The increase of their food supply, sebaceous glands, proliferate during puberty, which explains the increase of infestations of mites during adolescence. Twenty-five percent of the people who are up to 20 years old have mites, and 30% of people up to the age of 50 have mites. Of people that are between 80 and 100 years old, between 50%-100% have mites.[7] Hair follicles in all adults are infested, but the distribution of mites varies, which has a different impact on each person. Men are often more likely to be infested by mites than women because they have more sebaceous glands, thus producing more food for the mites.[8]
https://en.wikipedia.org/wiki/Demodex_folliculorum
Demodex Folliculorum, also know as Demodicids, are a species of tiny mite that some researchers have recently identified as a profound contributor to blepharitis, rosacea, dry eyes, eyelash loss, and hair loss. While we believe that there are other factors affecting those with blepharitis, rosacea, dry eyes, eyelash loss, and hair loss, such as diet, genetics, and other immune related issues, many researchers attribute this microscopic critter with much more than just a small role. Demodex has also been called “face mite” as it has been commonly associated with other various skin complications of the face, such as Acne Rosacea, blackheads, and other skin irritations.
Varying in size from .1mm to .4 mm long, it lives in your pores and hair follicles, typically on your scalp, cheeks, nose, eyebrows and often in the roots of your eyelashes. Demodicids have worm-like attributes, with tiny claws, and scales over the whole of its body so that it may better anchor itself in the hair follicle. An individual female may lay up to 25 eggs in a single follicle, and as the mites grow, they become tightly packed. When mature, the mites leave the follicle, mate, and lays more eggs. During the day, Demodex mites remain feeding within the follicle. At night, they emerge onto the surface to mate, and eggs are laid into follicles so that the newly hatched larvae may feed on sebaceous oils.