Cleansing your extensions won't necessarily prevent lice, but it will make it much harder for bacteria and mites (sorry) to grow and thrive. While you'll want to avoid oil and alcohol to keep your faux lashes in tact, you can use a cotton swab dipped in micellar water to cleanse them. Jennifer Tsai, OD , a Manhattan-based optometrist of Line of Sight Vision & Wellness, recommends a diluted tea tree oil cleanser for your extensions and lids (just be careful not to get it into your eyes).