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

To compare the in vitro anti-demodectic activity of four commercially available dedicated eyelid cleansers (Cliradex^® towelette cleanser, Oust™ Demodex^® cleanser, Blephadex™ eyelid foam, TheraTears^® SteriLid^® 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.

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.

The absolute concentration of terpinen-4-ol and the relative abundance of linalool in the four eyelid cleansers and tea tree oil were determined.

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^® was the only eyelid cleanser that demonstrated comparable antiparastic activity to 50% tea tree oil (p = 0.36).

Among the four eyelid cleansers, Cliradex^® contained the highest concentration of terpinen-4-ol, while linalool was present in TheraTears^® SteriLid^® only.

Of the four commercial eyelid cleansers, Cliradex^® demonstrated the highest levels of in vitro anti-demodectic 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.