Eyelash extensions do not damage your natural eyelashes. During your appointment, the lash technician will apply the extensions to your natural lashes using medical grade adhesive. Damage generally occurs if the placement was done incorrectly, or if the extensions used were too heavy for the lashes. Most people are able to handle a maximum thickness of 0.20mm. For our classic lashes, we typically use lashes with a thickness of 0.15mm or 0.18mm.