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Dispelling the Mystery of Demodex

Dispelling the Mystery of Demodex

 

Rosacea is not an infectious disease, and there is no evidence that it can be spread by direct contact with the skin of an affected patient or through inhaling airborne bacteria. However, there has long been a theory that parasites within the sebaceous follicles of the face can stimulate inflammation.

One such organism is the Demodex folliculorum mite, which studies have shown to be more prevalent and active in rosacea patients than in control groups. The mite is 0.3-mm long and is a part of the normal flora of most adults, but becomes a pathogen after it multiplies and invades the dermis, creating an inflammatory response. Aside from rosacea, it has been implicated in folliculitis, dyschromias, pityriasis folliculorum, and inflammatory blepharitis.1,2,3,4

Although there is not a standard assay for Demodex folliculorum or its smaller partner D. brevis, a controlled study revealed 10% of all skin biopsies and 12% of all hair follicles contained Demodex mites. This study also suggested that the prevalence of both species increased with age, but D. brevis had a lower prevalence.

The face was most heavily infested by both species, but D. brevis had a wider distribution on the body. Males were more heavily infested than females with both species, the difference being greater for D. brevis.3

Early vascular and connective tissue changes probably create a favorable setting for a growth of these mites. This may represent an important cofactor especially in papulopustular rosacea, in which a delayed hypersensitivity reaction may be operative, but it is not the cause of rosacea. On the other hand, clearing rosacea signs after oral tetracycline or sulfur ointment may not affect the resident Demodex population.2,4

The incidence of demodicosis is age related. It was found in approximately 25%, 30%, 50%, and 100%, in patients up to age 20 years, 50 years, 80 years and 90 years, respectively. In healthy persons, one can find one or more Demodex mites in every tenth eyelash. This index rises with increasing age. In blepharitis or other external eye diseases, Demodex mites are found in about every sixth eyelash. Therapy of chronic blepharitis in association with demodicosis may include antibiotics, corticosteroids, quicksilver 2%, permethrin, crotamiton or lindane. Massage of lid margins is essential because local treatment is not very effective as long as the mite remains deep in the pilosebaceous complex.4
 

The Incidence of Concomitant Demodicosis

According to a recent study published in the Journal of the American Academy of Dermatology, there is a high frequency of patients with rosacea who have concomitant “Demodicosis” that contribute to their clinical manifestations. In this study, 10 dermatologists observed 3,213 patients that presented with at least one to two diagnoses each. Each investigator found an average of 2.4 patients with demodicosis with variable severity of clinical findings. It was determined that demodicosis was the ninth most frequent diagnosis seen by this group, without a considerable bias of gender, season, age, or other contributing factors. The main observation was that all the patients were otherwise in good health. This same group suggested the use of treatment should include applying topical crotamiton 10% in the morning and crotamiton 10% plus benzyl benzoate 12% in the evening 2 to 3 minutes after facial cleansing. This regimen provides a directed antimicrobial (acaricidal) effect against the mite.4

A case report from 1999 reported efficacy against Demodex with oral ivermectin and topical permethrin cream.6 Researchers treated a 32-year-old man who presented with a chronic rosacea-like dermatitis of the facial skin and the eyelids that had resisted treatment for more than 4 years. They prescribed a one-time oral dose of ivermectin at 200 µg/kg and began topical permethrin weekly, which resulted in significant clearance.

In another case, a 2-week course of oral metronidazole was needed for what were considered Demodex abscesses on the face.7

Rosacea at a Glance

One of the most common facial dermatoses is rosacea, a chronic, relapsing and potentially life disrupting disorder that affects an estimated 14 million Americans. Many patients present with redness on the cheeks, nose, chin or forehead that often waxes and wanes — although a background of diffuse redness (“rouge erythema”) tends to persist indefinitely. The disease is more frequently diagnosed in women, but more severe symptoms tend to be seen in men.1

Facial burning, stinging and itching are commonly reported by many rosacea patients (see Figure 1). Some rosacea sufferers may also experience some swelling (edema) in the face that may become noticeable even early during the course of their disease.

It is also believed that in some patients this swelling process may contribute to the development of excess connective tissue on the nose (rhinophyma) or chin (gnathophyma).

It is often stated that fair-skinned patients who tend to flush or blush easily are at greatest risk of developing rosacea. Or, it may be that facial redness from rosacea is simply more obvious in lighter skin.

A physiologic or homeostatic blush may appear the same, as flushing secondary to ingestion of medications such as niacin or some antihypertension drugs.

Flushing occurs when a large amount of blood quickly flows through vessels and the vessels expand under the skin to accommodate the flow.

However, people with extensive chronic photodamage, and even treated rosacea patients can still present with a red face or diffuse telangiectasia, which are often misdiagnosed as active rosacea. This is because telangiectasias not only develop with rosacea, but they may have been pre-existent. There may be some residual persistence of redness from the dilation of blood vessels that occurred during active disease.

 

Defining Rosacea Subtypes and Highlighting the Triggers

Persistent erythema without the presence of inflammatory lesions is characteristic of erythematotelangiectatic (subtype 1) rosacea and also quiescent papulopustular (subtype 2) rosacea.

Treatments for diffuse “background” erythema or telangiectasia include camouflage makeup, sunscreens, vascular laser treatments, or intense pulsed light.

Rosacea remains a clinical diagnosis; there are no histological, serological or other diagnostic tests that are pathognomonic for rosacea.1,2 However, features of dermal matrix degradation characteristic of actinic elastosis are the most frequently reported histologic signs seen in biopsies of rosacea.

A thorough examination of signs (appearance of “bumps” or “pimples”) and symptoms (redness, flushing, and swelling, burning, itching or stinging) as well as a medical history of potential triggers lead to the diagnosis.

The National Rosacea Society suggests that the most common triggers of rosacea are sun exposure, emotional stress, hot or cold weather, wind, alcohol, spicy foods, heavy exercise, hot baths, heated beverages and certain skin-care products. In other words, almost anything that potentially stimulates vasodilatation of facial vessels is “bad news” for rosacea-prone facial skin.

Unfortunately, some conditions such as lupus erythematosus, seborrheic dermatitis, drug eruptions, lymphocytic infiltrate of Jessner, polymorphous light eruption, sarcoidosis, and even rare forms of lymphoma can simulate rosacea and are often missed by the untrained eye. In other cases, patients experience prolonged durations of these diagnoses as they are misdiagnosing themselves. 1,2

Using a Maintenance Regimen

As rosacea is characterized by flare-ups and remissions, and research has shown that long-term medical therapy significantly prolongs the duration of remission in rosacea patients, it behooves patients to use a maintenance regimen.

In a 6-month multicenter clinical study, 42% of those not using medication had relapsed, compared to 23% of those who continued to apply a topical antibiotic. Therefore, treatment between flare-ups can prevent them.

A rosacea facial care routine starts with use of a gentle facial cleanser each morning.2 Sufferers should use a mild cleanser that is not grainy, abrasive or astringent, and gently spread it with their fingertips. A soft pad or washcloth can also be used, but avoid rough washcloths, loofahs, brushes or sponges. The face should be rinsed with lukewarm water and gently blotted dry with a cotton towel.2

Typically, topical crotamiton cream is not part of the standard rosacea regimen prescribed by dermatologists unless the actions of Demodex are considered.3 Yet in 1981 it was suggested that mites will survive high concentrations of metronidazole, one of the mainstays of rosacea therapy, so the role of metronidazole was not linked to the mite per the authors.7,8

A New Treatment Option

A new treatment available is seabuckthorn oil (Hippophae rhamnoides). Its activity is targeted against the mite to reduce the inflammation under the skin and therefore provide relief of the mechanisms that cause the rosacea complex of symptoms.

The advantage patients find with the cleanser is the elegance of the vehicle in otherwise sensitive skin, the presence of vitamin E and aloe vera, which may provide additional therapeutic properties, and other active ingredients such as astragalus membraceus and spirodela polyrhiza, potentially useful yeasts that are suggested to augment the activity of seabuckthorn oil.

 

Using Intense Pulsed Light

Several reports that have advocated the use of intense pulsed light (IPL) for the treatment of acne also suggest some efficacy against Demodex.

Dr. Neil Sadick of Cornell University in New York, conducted an investigation of 24 patients with a mean age of 47 years and Fitzpatrick skin types I-IV. He treated them with an IPL device (Quantum SR, ESC-Lumenis), which emits a noncoherent, multiwavelength of light of 500 nm to 1,100 nm. Patients were treated monthly, up to five times, using an average fluence of 25 to 45 J/cm2. At a recent conference he reported that IPL appears to kill mites around hair follicles and sebaceous glands, which could make it useful in treating rosacea. However, the use of this device in other conditions is not yet standard of care, and these procedures should be performed under dermatologic supervision.5

Looking Ahead

Rosacea is a very common condition, as we’ve mentioned, and the involvement of the Demodex mite remains a strong correlation in some patients — although not a definitively proven link. As dermatologists, we have several therapies we can rely on to treat rosacea and Demodex mites, including some newer therapies that appear promising.

 

 

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