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DEMODEX FOLLICULORUM

RESEARCH INTO DEMODEX – Dr Monika Udziela MD, Dr Mariusz Rowiński

Demodex folliculorum (of the Demodecidae family) belongs to the mites class, and has recently been the subject of increasing interest among doctors.

The knowledge and information flowing in recently shows that

these microscopic mites should be taken into consideration by people with

ophthalmological and/or dermatological conditions.

Demodex are external parasites, two species of which live on humans:

Demodex folliculorum and Demodex brevis.

They both dwell in hair follicles and sebaceous glands in the skin of the face, where they feed on fats and sebum discharges.

They are most concentrated around the nose and eyes, and on the forehead and chin, sometimes they can live on other parts of the body, e.g. the skin of the hands or feet.

Ophthalmologists are increasingly considering that patients with chronic inflammation of the margins of the eyelid may have demodex, while dermatologists may suspect that it is a factor behind acne rosacea.

These conditions often co-occur, which would be easily explained if both were caused by the same pathogen.

Frequency of demodex infection increases with age, which is probably due to reduced immunity in older people.

It is very rare among children, mainly affecting those with immunological disorders.

Infection with demodex mites occurs through contact, and probably through dust which may contain their eggs.

They cannot be contracted from animals as demodex displays species homogeneity.

Clinical profile

The medical condition caused by the presence of demodex is called demodectosis.

The symptoms of demodectosis are a result of the following processes:

clogging of the hair sheaths and tubules leading from the sebum glands, reactive hyperkeratinisation and hyperplasia of the epithelium, mechanical transfer of bacteria and/or fungus (secondary bacterial/fungal infection), inflammatory reaction of the host to the presence of chitin, stimulation of immunological reactions due to the presence of mites and their discharges.

The condition is often misdiagnosed as allergic inflammation or a bacterial or fungal infection.

Demodex living in the hair follicles of the eyelids causes persistent, chronic

inflammation of the margins of the eyelids (blepharitis) and sometimes of the conjunctiva (blepharoconjunctivitis).

Demodex moving in the hair sheaths mechanically irritate the papilla and bulbs and their metabolic products cause chemical irritation and distension of the bulbs.

This results in a clinical profile with inflammation of the margins of the eyelids, visibly distended blood vessels on the eyelids and capillaries entwining the hair sheaths.

As the parasite grows in the follicles, the base of the eyelashes may shift and grow in a different direction.

One of the common symptoms of demodex infection is excessive eyelash loss.

Changes caused by demodex may sometimes occur without distinct pathological features.

Some patients may display relatively uncharacteristic or non-specific symptoms.

Patients mainly complain about stubborn itching, burning and reddening eyelids.

Demodex is often misdiagnosed as allergic inflammation or a bacterial or fungal infection.

Only a lack of improvement after long-term treatment of these conditions

would lead to consideration of a different cause of chronic inflammation of the margins of the eyelids, often with complications on the surface of the eye.

Detecting the presence of demodex is neither difficult nor invasive.

It is done by taking several eyelashes from the patient, which often come out very easily.

The lashes are placed in an appropriate preparation which is then carefully tested by microscope.

The decision as to the treatment method is taken by the ophthalmologist based on the results of the parasitology test and the clinical profile.

The therapy lasts several months (minimum 2 months) and requires systematicness and good cooperation between the doctor and the patient.

An assessment of the effectiveness of the treatment and possibility of

a relapse require parasitology check-ups.