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) explains the increase of infestations of mites during adolescence. 25% 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% and 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]

A 2014 study conducted at North Carolina State University found that 100 per cent of 253 people over age 18 sampled by her team had mite DNA on their faces, suggesting that the mites could be universal inhabitants of adult humans.[11]