Demodex – An invisible world
Many scientists agree that Demodex mites, in particular, Demodex folliculorum mites, which are present on or within our skin, may possibly be responsible for the onset of rosacea.
Despite the fact that the pathogenetic mechanisms of rosacea are not known, various causative factors have been put forward. A large number of studies have been conducted in the past decades to examine the possible correlation between the pathogenesis of rosacea and the presence of certain microorganisms or bacteria, which exist on or within the skin.
According to the results of a large number of studies, Demodex mites, which host bacteria, may play a significant pathogenetic role in rosacea, on the one hand, when present in large quantities and on the other hand because of an imbalance of the immune mechanism. When facial fat substances composition changes, mites grow, as they are overtaken by these. At the end of their life cycle, they release a lot of bacteria, leading to the onset of rosacea.
Demodex mites and their role
Demodex, (small organisms) are inhabitants of the sebaceous follicles of the adult facial skin. These mites were first described in human skin in 1800, but their potential for a beneficial function is still unknown. They transport bacteria on the skin surface and their population can increase remarkably in certain circumstances. They can be easily extracted from the follicles where they are found, often in groups, head downward, feeding on sebaceous material. They possess four pairs of short stubby legs with claw-like appendages, which they use to move at night (Demodex mites react negatively to light) about the facial skin surface from one follicle to another.
Demodex mites seem to enjoy harmonious relationships with their hosts and usually do not excite an inflammatory reaction in the epidermis. Their possible useful role in human skin remains a matter of controversy, and it is probably impossible to fully eradicate them as the skin seems to become rapidly recolonised even after an anti-mite treatment.
The number of Demodex folliculorum is high in the skin of patients with rosacea and found mainly in the centro-facial convexities – the areas typically affected by the inflammatory papules and pustules.
Histologic sections of inflammatory lesions show the pathologic changes to be centered in the hair follicles on the face where Demodex mites live and are often surrounded by inflammatory cells. Sometimes ruptured follicles are seen with particles of Demodex mites extruded into the dermis. Immunosuppressed patients (with HIV infection or on immunosuppressive therapy or patients having renal dialysis) or those who have applied immune-modulating drugs (topical steroids/calcineurin inhibitors) to the face may also have increased numbers of Demodex mites on the skin. Some immunosuppressed patients may also develop a pustular eruption similar to rosacea with multiple mites identified not only on skin biopsies but also visualised by microscopic examination obtained by gently scraping the skin surface.
Finally, it has been shown that Demodex mites carry bacteria, some of which are susceptible to the antibiotics used to treat the papules and pustules of rosacea acne. Another recent finding which may have relevance to the understanding of the papulopustular rosacea is the discovery that antimicrobial peptide (AMP) production and/or metabolism appear to be altered in patients with rosacea. These peptides or related enzymes can produce inflammatory lesions similar to the papules and pustules of papulopustular rosacea. It may be that this new knowledge will provide insight into the causation of rosacea in the future.
Demodex detection in our dermatology clinics
Demodex colonisation in the human population is high (20 – 80%) and it increases with age, reaching up to 100% in elderly people. Demodex mite infestation usually remains asymptomatic, further intensifying the problem of non-diagnosis. It is of utmost importance to perform the special examination for the detection of the mite so as to provide an effective treatment for the management of rosacea.
In our dermatology clinics, rosacea diagnosis is performed according to the clinical features of the skin, and the use of the advanced skin analysis system Canfield VISIA® (Canfield Scientific, Inc., New Jersey, U.S.A.). Furthermore, since the aetiology of rosacea is associated with the presence of bacteria and Demodex mites, microscopic examination is also suggested. The examination is performed in the special microbiology laboratories of our clinics and within ten minutes it is determined whether the mite is present.
Depending on the laboratory findings, the appropriate treatment regimen is recommended with special miticides, such as crotamiton and permethrin. In some cases, phototherapy is also used in combination, which has double action on Demodex folliculorum. More specifically:
- With the red light spectrum (633 nm)anti-inflammatory action is achieved, i.e. reduction of inflammation.
- With the blue light spectrum (415 nm)anti-bacterial action is achieved, as it acts against the mites’ bacteria. Therefore, it is possible to manage rosacea effectively.
If you think that you may have rosacea, you should not ignore the warning signs, but instead visit a dermatologist as soon as possible, for proper diagnosis and the appropriate medical treatment before the condition becomes worst.