The only way to distinguish between Demodex dermatitis and rosacea or other common dermatoses is an empirical trial of treatment for the Demodex mite, says an expert who believes emphatically that this mite does not cause rosacea.
"Any patient who presents with a red face - especially a red, dry, scaly face - should have an empirical trial of a topical or systemic medication to treat Demodex," says Joseph Bikowski, M.D., director, Bikowski Skin Care Center, and clinical assistant professor of dermatology, Ohio State University, Columbus, Ohio.
"There are three distinct facial dermatoses of consequence - rosacea, seborrheic dermatitis and Demodex dermatitis," he says. All three occur commonly, and commonly cross over, so that a patient can have more than one at a time, adds Dr. Bikowski, who says his conclusions are based on anecdotal evidence.
Demodex dermatitis and rosacea are entirely separate clinical entities, Dr. Bikowski tells Dermatology Times, "and I believe there are numerous patients who present with red, scaly faces who have rosacea in combination with either seborrheic dermatitis or Demodex dermatitis. They could also have seborrheic or Demodex dermatitis alone," he says.
One study has shown that 10 percent of skin biopsies and 12 percent of hair follicles contain Demodex mites. The same study shows that both Demodex folliculorum and the smaller D. brevis exhibit their heaviest infestations on the face (Aylesworth R, Vance JC. Demodex folliculorum and Demodex brevis in cutaneous biopsies. J Am Acad Dermatol. November 1982; 7(5):583-589).
However, Dr. Bikowski says that if one performs a potassium hydroxide (KOH) preparation of the facial skin and examines it for mites microscopically, "Even if the sample is negative, it does not mean the patient does not have Demodex dermatitis. And just because the scraping is positive, it does not mean the patient has Demodex dermatitis."
Indeed, dermatologists generally consider the D. folliculorum mite a normal part of the human flora that only becomes a pathogen after it multiplies and invades the dermis, provoking an inflammatory response (Bhatia B, Del Rosso JQ. Acne & rosacea: just the facts - dispelling the mystery of Demodex. http://www.skinandaging.com/article/6756/).
Accordingly, Dr. Bikowski says, "At this point in time, the only way to determine if a patient has Demodex dermatitis is through an empirical trial of one of three medications."
Those medications are topical Elimite (permethrin, Allergan), topical Eurax (crotamiton, Ranbaxy) or systemic ivermectin.
When a patient who has had no previous treatment presents with a red, scaly face, he says, "The first thing one should do is discuss skincare. Skincare to me means cleansing and moisturizing with a product that contains ceramide," which helps restore the skin barrier. "No matter which of these diseases is involved," Dr. Bikowski says, "the skin barrier is disrupted."
As a next step, he continues, "I always do KOH preparation just to see if I can find the Demodex mite."
Whether he finds this mite or not, Dr. Bikowski says, "I undertake an empirical trial, usually with crotamiton, used twice daily for two weeks as indicated."
If the patient's skin improves dramatically after two weeks, he says, "This probably proves that at least part, if not all, of the disease process is Demodex dermatitis."