Chicken or Egg? Debate Continues
Demodex mites, the microscopic parasites that are normal inhabitants of facial skin, have long raised the question, "Which comes first, Demodex or rosacea?" as medical experts debate whether their increased numbers on rosacea patients are a cause or a result of the disorder. Now there may be some evidence that the "chicken" — Demodex mites — and not the "egg" comes first, according to a recent scientific report.
In an article in the Journal of the European Academy of Dermatology and Venereology, researcher Dr. F.M.N. Forton has championed the mite as a key culprit behind the development of the condition, noting it may be the missing link in understanding the onset of subtype 2 (papulopustular) rosacea, characterized by redness with bumps and pimples.1 She noted that National Rosacea Society-funded research has shown that toll-like receptors (TLRs) trigger production of cathelicidins, components of the immune system that may prompt subtype 2 rosacea.
She further noted that the two factors that stimulate the TLRs to induce cathelicidins are skin infection and disruption of the skin barrier. These conditions occur when Demodex mites are present, and she contends that the increased number of Demodex mites may therefore be a cause rather than a result of the bumps and pimples.
The link between mites and infection may be suggested by evidence that the complaint of sensitive skin in rosacea patients disappears when the number of Demodex mites is brought back to normal, she said. Disruption of the skin barrier may also occur as the mites erode the skin surface, penetrating into the lower dermis skin layer.
Furthermore, Dr. Forton suggested the Demodex mites themselves may be responsible for the bumps and pimples of subtype 2. Biopsies have shown that the presence of Demodex mites inside facial follicles consistently corresponds with the immune response in the skin as the body protects itself against invaders.
She noted that bumps and pimples — a sign that the body's immune system has kicked in — may appear when the mites are already on their way out after treatment. This suggests that the mites trigger the immune process that produces the bumps, rather than simply gravitating toward them after they appear.
Topical therapies are known to potentially reduce the number of mites, and Dr. Forton concluded that confirming a role for Demodex introduces the possibility of advances in treatment.
In mild to moderate cases, doctors often prescribe oral and topical rosacea therapy to bring the condition under immediate control, followed by long-term therapy to maintain remission. In severe cases, higher doses of oral antibiotics or other drugs may be prescribed.
- Forton FMN. Papulopustular rosacea, skin immunity and Demodex: pityriasis folliculorum as a missing link. Eur Acad Dermatol Venereol 2012;26:19-28.
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