Answering your questions

Jan. 13, 2014

Editor’s note: Anthony Kurec, MS, H(ASCP)DLM, answers a question from a reader. Anthony is Clinical Associate Professor, Emeritus, at SUNY Upstate Medical University in Syracuse, NY, and a member of the MLO Editorial Advisory Board.


We found a Demodex folliculorum mite in a routine UA. Is this common? Should we report it out? Thank you for you help.


The literature does not cite any evidence that this is a common or even a rare event. There does not appear to be any indication that this occurs with any frequency at all. Because this mite is ubiquitous on human adults, it would seem that the presence of this particular mite found in the urine was one of contamination. As noted below, large infestations of this mite can exist, and it would seem that its presence elsewhere other than the skin, as in this case, is most likely due to dislodgement of the mite from the skin area. It would be useful to get some history on this patient to see if he or she falls within the type of cases that have been associated with this mite or if there is some other circumstance that is unique to this patient.

The decision to report this is one your medical director should make; however, if it is reported, a note of explanation might be in order. Demodex folliculorum and Demodex brevis are the two species of mites that are almost exclusively found on human skin, specifically near the facial sebaceous follicles.1,2 These mites have a short life cycle (average of 14.5 days), are negatively phototaxic (mobile only in the dark), and are thought to be generally in symbiosis with their host by ingesting bacteria or other organisms in the sebaceous canal.3 While usually not found on infants or young children, these mites will normally colonize on most human adults, generally causing no complications.

They are nocturnally mobile (16 mm/hour); thus, once the female mite is impregnated at the opening of a hair follicle, she moves to the sebaceous gland to deposit her eggs. They form larva that eventually mature by making their way to the skin surface, only to re-enter the hair follicle to become an adult.3 Demodex generally inhabit the skin of the cheeks, forehead, nose, chin, and external ear, living off sebum secreted by the sebaceous glands. The mites can also be found on eyebrow and/or eyelashes. They are easily susceptible to desiccation and thus have limited ability to live off the body.3

In healthy adults, Demodex does not usually cause any health problems. However, when their numbers increase, various skin problems have been noted.1-3 Facial rosacea is the most common skin problem associated with this mite, though it has been seen with other types of skin problems, such as skin flaking, dermatitis, facial pigmentation, skin eruptions, and basal cell carcinoma.3 Individuals who are immunocompromised (chemotherapy, HIV, AIDS), who are undergoing phototherapy or chronic dialysis, or who have type 2 diabetes have also been associated with the presence of Demodex.3,4

In rare cases, Demodex folliculorum has been shown to inhabit the scalp, chest, nipple, penis, mons veneris, buttock, and buccal mucosa.5,6 Though the presence of the mite in the genital skin area is not a commonly reported problem, that could explain its appearance in a freely voided urine if appropriate collection protocol was not followed and the mite was inadvertently displaced.


  1. Lacey N, Raghallaigh SN, Powell FC. Demodex mites—Commensals, parasites, or mutualistic organisms? Dermatol. 2011;222(2):128-130.
  2. Kligman AM, Christensen MS. Demodex folliculorum: requirements for understanding its role in human skin disease. J Invest Dermatol 2011;131(1):8-10.
  3. Lacey N, Kavanagh K, Tseng SCG. Under the lash: Demodex mites in human diseases. Biochem. 2009;31(4):2-6.
  4. Gokce C, Aycan-Kaya O, Yula E, et al. The effect of blood glucose regulation on the presence of opportunistic Demodex folliculorum mites in patients with type 2 diabetes mellitus. J Internatl Med Res. 2013;41(5):1752-1758.
  5. Ugras M, Miman O, Karincaoglu Y, et al. The prevalence of Demodex folliculorum on the scrotum and male perineal skin. Turkyie Parazitoloji Dergisi 2009;33(1):28-31.
  6. Hwang SM, Yoo MS, Ahn SK, et al. Demodecidosis manifested on the external genitalia. Internl J Dermatol. 1998; 37(8):633-640.