Eyelash Extensions are semipermanent lashes. One individual eyelash extension or one fan of eyelash extensions is applied to one of your natural lashes. They are safe when done correctly by a trained professional and can encourage your natural lashes to grow longer. Eyelash extensions replace the need to wear mascara, eyeliner, sometimes even eye shadow. Beauty by Lindsey K clients save up to 10 minutes in their morning routines.