Cleansing your eyelash extensions daily with a specially-formulated lash cleanser is key to achieving great retention of your eyelash extensions. Please ensure to ask your lash tech what you should be using. Not everything you see advertised on the internet is acceptable. Thoroughly cleansing your lashes prevents the build up of any impurities- such as dirt, oils, environmental impurities + dead skin cells. If lash extensions are not cleaned properly, a condition called blepharitis can occur. Natural lashes and extensions love clean lashes! It is possible your lash technician may recommend a lash serum only if needed. Again, please avoid what you see on the internet. Not all serums can be used with lash extensions.