Modern Lash Eyelash Extensions add length, thickness and fullness to natural eyelashes. They are made with the finest material and the adhesive is surgical-grade. Extensions come in a variety of lengths and thickness. Modern Lash eyelash extensions can be worn during sleep, showering and swimming, however, excessive exposure to oil can weaken the bond. Eyelash extensions differ from “fake” or “false” eyelashes in that they are applied to each individual eyelash. Eyelash extensions may last from two weeks to one month, depending on the cycle of hair growth. As your eyelashes grow out, it cycles and falls out naturally, thus shedding the extension with it.