The in vitro Effect of Various Selenium Disulfide Concentrations on Demodex Folliculorum

Abstract

Purpose : To evaluate the effectiveness of varying concentrations of selenium sulfide in affecting Demodex folliculorum.

Methods : Sixty-five eyelashes with live Demodex from 29 patients seen at the Nassau University Medical Center (17 patients) and Ophthalmic Consultants of Long Island (12 patients) were observed for 90 minutes under 0.1%, 0.5%, 1.0%, and 4.0% selenium sulfide with either carboxymethyl cellulose (CMC) solution or vaseline ointment as excipients. Positive and negative controls were also evaluated as separate solutions of CMC, vaseline, basic saline solution, 50% tea tree oil, and 100% tea tree oil.

Results : Demodex behavior was affected by concentrations as low as 0.1%. Deaths in the selenium sulfide reagents were observed in the the 4.0% selenium sulfide solution with CMC (36.4% kill rate, 4 of 11 Demodex, average time of death 17.5 minutes) and 4.0% selenium sulfide with vaseline ointment (12.5%, 1 of 8 Demodex, time of death 75 min). No Demodex deaths were witnessed in the other treatment groups. However, Demodex mites in concentrations as low as 0.1% were noted to move away from the selenium.

Conclusions : Selenium sulfide has shown efficacy in killing Demodex at a 4% concentration with the CMC solution and mild cidal activity with 4% vaseline. Concentrations as low as 0.1% show avoidance by Demodex folliculorum suggesting that it might function as a natural insect repellent.

This is a 2021 ARVO Annual Meeting abstract.