In vitro anti-demodectic effects and terpinen-4-ol content of commercial eyelid cleansers

Purpose: To compare the in vitro anti-demodectic activity of four commercially available dedicated eyelid cleansers (Cliradex (R) towelette cleanser, Ousr (TM) Demodex (R) cleanser, Blephadex (TM) eyelid foam, TheraTears (R) SteriLid (R) eyelid cleanser), tea tree oil, undiluted terpinen-4-ol and linalool; and to assess the terpinen-4-ol content of the commercial cleansers and tea tree oil. Methods: In vitro anti-demodectic efficacy assessment: 93 viable Demodex mites were acquired from the epilated eyelashes of 10 participants, and were randomised to application with one of the four eyelid cleansers, 100% and 50% tea tree oil, undiluted terpinen-4-ol and linalool, or no treatment. Following treatment application, mite viability was assessed for 300 min, based on limb/body movement and/or the development of a crenated/translucent appearance. Kaplan-Meier survival analysis was then performed. Mass spectrometry analysis: The absolute concentration of terpinen-4-ol and the relative abundance of linalool in the four eyelid cleansers and tea tree oil were determined. Results: In vitro anti-demodectic efficacy assessment: No significant differences were observed between undiluted tea tree oil, terpinen-4-ol and linalool (all p > 0.05). Although all commercial eyelid cleansers effected lower mite survival probabilities than the untreated group, Cliradex (R) was the only eyelid cleanser that demonstrated comparable antiparastic activity to 50% tea tree oil (p = 0.36). Mass spectrometry analysis: Among the four eyelid cleansers, Cliradex (R) contained the highest concentration of terpinen-4-ol, while linalool was present in TheraTears (R) SteriLid (R) only. Conclusions: Of the four commercial eyelid cleansers, Cliradex (R) demonstrated the highest levels of in vitro antidemodectic activity and terpinen-4-ol content Undiluted linalool and terpenin-4-ol showed comparable antiparasitic efficacy, and the use of linalool in the management of demodectic blepharitis warrants further investigation.