What Is a Demodex Mite?

Demodex is a genus of common mite that lives on the skin surface, feeding on sebum that is excreted from the hair follicles and sebaceous glands. The two species that are commonly found on humans are Demodex folliculorum and Demodex brevis. Both are referred to as eyelash mites or face mites, but they can be found anywhere on the body. One further species that is found less commonly on humans is Demodex canis, the Demodex mite of the domestic dog. It tends to only be found on humans with immunosuppressive conditions. The feline equivalent, Demodex cati, has not been reported from humans.

Demodex mites are tiny: less than half a millimeter long. They generally don’t cause any problems, but as with a lot of symbiotes and ectoparasites (parasites that live on the outside of the body), if their population builds up, then health issues can occur. Blepharitis (inflammation, scaling and reddening of the eyelids) and demodicosis (a rosacea-like skin condition associated with inflammation of the hair follicles) are two examples of skin conditions directly related to Demodex infestation.

When Do Infestations Occur?

Infestations are most likely to occur if people have suppressed or challenged immune systems, for example due to HIV, cancer, liver disease, or corticosteroid use. However, they can occur in other circumstances, as described in “Demodicosis Associated with Wearing a Face Mask: A Case Report”.

How Can Infestations Be Treated?

Treatment includes topical insecticides or the oral anti-parasitic drug ivermectin. If an infestation is diagnosed early, it may be possible to deal with it using specialized facial wipes for Demodex or even gentle surfactants like baby shampoo. Changes in behavior can also be needed: avoiding oily skin products and cosmetics, for example.

Can Surgical Masks Cause Imbalances in Demodex Populations and Other Skin Problems?

The case described in “Demodicosis Associated with Wearing a Face Mask: A Case Report” deals with a case where behavior rather than immunosuppression led to a Demodex infestation. It’s a behavior that we have all experienced in the past few years: wearing a surgical face mask.

Wearing a face mask for over one hour can cause an increase in skin temperature and sebum excretion in some people. It can also cause the skin to become drier. It would be rare to see any significant issues in an individual with healthy skin after one or two hours. However, wearing a mask for longer continuous periods has been associated with issues in many people, with 5 or 6 hours often cited as the problem point. Skin conditions associated with face mask use include atopic dermatitis, acne, and rosacea.

How Often Should You Change Your Mask?

Public health advice in many countries is that you should change your mask once every four hours, preferably cleaning the face during the change, and not re-use masks over multiple days. It doesn’t matter whether it’s a cloth mask or a surgical mask, the result can be the same from excessive use.

What Is the Report About?

The report is from the first case of demodicosis associated with wearing a face mask. The patient in this case was wearing a surgical mask (at first) and a cloth mask (after suspecting an allergy to something in the surgical mask) for over 8 hours per day for three weeks. The patient was helped by treatment with ivermectin and behavioral changes (avoiding wearing the same mask continuously, using a new mask every day). This quickly cleared up the issue.

The author recommends that demodicosis be included in the differential diagnosis for facial rashes associated with face masks during the COVID-19 pandemic. And we can all take care to change our masks after 4 hours and keep our faces clean using gentle surfactants during the ongoing health measures for COVID-19.