There are numerous mites, bacteria and fungi that reside on or in our skin’s outer layers (epidermis). Some are helpful in maintaining skin pH or preventing other harmful microbes from establishing themselves. Others such as Ringworm (Tinea), head lice or scabies are not ‘host friendly’ and their presence will result in intense skin irritation or infection.
Fungal or mite infestation (Demodex Canis) is a more common cause of mange in animals; in fact Alopecia areata originates from the Greek word ‘Alopekia’ – the term used to describe how wild foxes with mange shed their pelt.
One form of mite increasingly thought to be a factor in hair loss from the head – scalp and face is Demodex Folliculorum – also known as Demodicids. Demodicids is a class of microscopic face mite related to scabies, bed lice and Pediculosis Capitis/Pubis – the common human head and pubic lice.
Demodicids is not generally well-known outside Dermatology but believed to be associated with various skin complications of the face, such as Acne Rosacea, some Acne Vulgaris (pustules or blackheads); Folliculitis* or inflammatory areas where hair follicles predominate (such as eyebrows & eyelashes).
Demodicids have worm-like attributes and – as with Pediculosis – claws and scales over its entire body so it may better anchor itself in or to the hair follicle. Typically they are 1-4 mm in length and spend their entire life cycle in skin appendage openings – the pores of our skin (sweat and sebaceous glands) and hair follicles.
Predominant area of infestation is the scalp or cheeks, nose, eyebrows, and roots of the eyelashes of the face.
Female Demodicids put down up to 25 eggs in a single follicle which becomes tightly packed as the mite larvae matures. This exhibits as redness, itching, irritation, blackheads, pustules or even discharge to the host’s scalp or face. Demodicids feed on sebaceous gland oil, the host’s body sweat, or skin cell debris.
As with other forms of mite Demodicid are relatively dormant during the day where they tend to remain within the follicle or skin pore to feed. They become active at night, emerging onto the skin surface to mate and lay more larvae eggs – and the Demodicid mite cycle continues.
Treatment considerations: Unfortunately it’s only recently that patients presenting with symptoms of Demodicid infestation have been seriously assessed. To be told one is picking at or scratching at their face and pulling ‘worms’ from under their skin might relate as more of a psychiatric issue than dermatological.
A biopsy of a suspect appendage or skin area should provide definite proof of Demodicid infestation. A combined oral antibiotic to treat mites and topical treatment such as those used for head lice or scabies usually kills the mites and hatching larvae.
* Including Folliculitis Necrotica
Copyright Anthony Pearce 2015 (revised April 2021)