Individual lashes are dipped into a medical-grade adhesive and bonded to your natural eyelash. This process is done one lash at a time. The extensions may be made from materials including mink, synthetic, or human hair. The adhesive can last about 4-6 weeks depending on how careful you are. The more you rub your eyes, wash your face, etc. Eyelash extensions are used to enhance the length, curliness, fullness, and thickness of natural eyelashes.