DESCRIPTION L'Oreal Paris Clinically Proven Lash Serum Strengthen, repair & beautify your eyelashes in just 30 days with L'Oreal Paris Clinically Proven Lash Serum! This eyelash serum is fortified with lash-loving ingredients like hyaluronic acid, biotin, keratin, and castor oil to help promote healthy lash growth. How This Eyelash Serum Works L'Oreal Paris' Clinically Proven Lash Serum is designed to improve the look and health of your lashes. The lash serum contains a unique blend of ingredients that work together to help strengthen and condition your lashes. The main active ingredient in the serum is keratin, which helps the growth of your eyelashes .