In vitro demodicidal activity of commercial lid hygiene products

Demodex folliculorum is a ubiquitous mite that can infest the eyelash follicles. Two commercial lid hygiene products have asserted their effectiveness in killing Demodex mites, yet there has never been a comparative trial between these two products. This study evaluated the demodicidal activity of 0.01% hypochlorous acid (HOCl) solution (Avenova; NovaBay Pharmaceuticals; Emeryville, CA) and 4% terpinen-4-ol (T4O) solution (Cliradex, Bio-Tissue; Miami, FL) in comparison to mineral oil (MO), a negative control.

Live Demodex mites were obtained from volunteers. Samples were immersed in 1-2 drops of test solution: 0.01% HOCl, 4% T4O, or 100% MO. Samples were observed under the microscope every 10 mins for up to 90 mins. Kill time was defined as the elapsed time between the addition of test solution and all cessation of movement of the body, legs, mouth and pedipalps for a minimum of 60 seconds.

T4O demonstrated a mean kill time of 40±0.0 mins. HOCl had a mean kill time of 87.86±4.23 mins, with 79% of samples surviving the full 90 mins. In the MO group, all samples survived through the 90 min mark. Kill time was statistically significant in favor of T4O as compared to HOCl (p=0.0005). There was no statistically significant difference in kill time between HOCl and MO (p=0.25).

4% T4O effectively killed all adult mite samples within 40 mins of exposure. In contrast, the demodicidal activity of 0.01% HOCl was minimal, and comparatively similar to 100% MO.