According to the Society for the Advancement of Education, 96 percent to 98 percent of people have mites in their hair. Mites are microscopic bugs that generally live in harmony with their human hosts. These tiny parasites feed on hormones, oils and fluids around the hair follicle. A single hair follicle can support a family of 25 mites. These teeny freeloaders may contribute to problems in some people including acne, hair loss, rosacea, dermatosis, rash and various other skin conditions. Elderly persons and people with cancer, compromised immune conditions such as HIV/aids and stress are particularly vulnerable to mites' potential noxious effects. Those who respond adversely may do so because their immune system is unable to respond sufficiently to keep the mite population in check or because of their inflammatory response to bacteria or waste products associated with the mites.
Demodex folliculorum, also called the follicle mite, lives in the hair follicles of humans and animals. It is considered a face mite because it is commonly found in the face. It spreads by direct contact or by eggs that are contained in dust. This mite is the most widely prevalent human mite and can be found on people throughout the world. The follicle mite generally produces no significant negative effects in most people, though it has been implicated in acne and blackheads due to the blockage of follicles. According to the National Institutes of Health, it has also been incriminated in chronic blephartis, a condition of inflammation of the eyelashes that can cause loss of eyelashes, eyelid scaling and itchy eyes or eyelids.
Demodex brevis is a second species of Demodex mites that makes itself at home in humans. While it is similar to the Demodex folliculorum in many respects, it generally leaves the follicles to the Demodex folliculorum, and instead lives and reproduces in the sebaceous glands of humans. Sebaceous glands, found at the root of hair follicles, produce oil to lubricate the skin. At .3 to .4 mm, Demodex brevis is slightly shorter than the Demodex folliculorum, but is implicated in some of the same conditions including acne, blackheads, and blephartis. Though less prevalent, it has a wider distribution on the body, according to Journal of the American Academy of Dermatology.
Demodex canis--commonly called mange, red mange or puppy mange---is considered to be a species specific mite that primarily resides on dogs. Though they prefer dogs, these mites can also be found in humans. They live and breed in hair follicles, and, like Demodex mites, don't usually trigger adverse reactions in humans.
Sarcoptes scabiei, also known as the scabies mite, can affect the scalp and cause hair loss, but actually lives in the skin. It is spread through close contact with infected persons, or occurs in crowded conditions where there is body contact. The closely related canine variant of Sarcoptes scabiei creates a condition of hair loss in dogs called sarcoptic mange, which also infects humans, according to Pet Education. However, the disease is self-limiting in humans and typically results only in temporary itching.