At some early point in their education, every medical professional learned Hickam’s Dictum—a somewhat droll principle stating that patients “can have as many diseases as they damn well please.” Focus that concept onto mites that feed off human skin cells and you may start to understand a new study on blepharitis and facial demodicosis. That research shows palpebral and facial Demodex infestations can co-exist, and many patients with Demodex-induced blepharitis also have elevated populations of facial mites.

The investigators—a pair of optometrists from Montreal—oversaw a double-masked cross-sectional study of 58 participants who underwent a standardized skin-surface biopsy and a lash epilation for each lid to obtain the forehead Demodex densities and the overall lash mite counts, respectively. In addition to the 19 patients in the control group, 21 were placed in the mild-to-moderate group and 18 in the severe group. All the patients had facial photographs taken to evaluate facial erythema and other dermatological issues. They each were evaluated using the ocular surface disease index (OSDI), non-invasive break-up time (NIBUT), tear meniscus height and bulbar conjunctival redness. Subjects were also asked about whether they noticed their eyes being watery or itchy, particularly along the lids.

The investigators found both the mild-to-moderate and severe Demodex blepharitis groups had cut-off values that confirmed facial demodicosis while the control group’s values were below the level of confirmation. Group comparisons showed that an increased severity of Demodex blepharitis was associated with higher forehead mite densities and increased lash mite count. The degree of facial erythema also positively correlated with forehead mite densities. The mild-to-moderate group reported more watery eyes and itching, and testing demonstrated lower tear meniscus heights than the control group.

This told the researchers three things: Demodex blepharitis is associated with facial demodicosis, itching along the lid margin is more specific to Demodex blepharitis than ocular itching and facial erythema may be an indicator of Demodex infestation.

Aumond S, Bitty E. Palpebral and facial skin infestation by Demodex folliculorum. Cont Lens Anterior Eye. September 25, 2019. [Epub ahead of print].