Evaluation of a novel treatment, selenium disulfide, in killing Demodex folliculorum in vitro

Objective: To evaluate the effectiveness of varying concentrations of selenium sulfide, an active ingredient in antidandruff shampoo, in killing 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 under light microscopy for 90 minutes in 0.1%, 0.5%, 1.0%, and 4% selenium sulfide with either carboxymethyl cellulose (CMC) solution or petroleum jelly ointment (Vaseline, Unilever, London) as excipients. Positive and negative controls also were evaluated as separate solutions of CMC, petroleum jelly, basic saline solution, 50% tea tree oil, and 100% tea tree oil. The number of Demodex deaths and time of death were recorded. Results: Demodex deaths in the selenium sulfide reagents were observed in the 4% selenium sulfide solution with CMC (36.4% kill rate, 4 of 11 Demodex, average time of death 17.5 minutes, p = 0.038) and 4% selenium sulfide with petroleum jelly ointment (12.5% kill rate, 1 of 8 Demodex, time of death 75 minutes, p = 0.351). No Demodex deaths were witnessed in the other selenium sulfide treatment groups. All Demodex died in the 50% and 100% tea tree oil positive control group. Conclusions: Selenium sulfide has shown efficacy in killing Demodex at a 4% concentration with the CMC solution and mild activity with 4% petroleum jelly. More research on selenium sulfide solutions at higher concentrations is indicated.