I’ve taken to adding Hylauronic Acid serum from The Ordinary to my castor oil and shake. I do this because there is some anecdotal evidence that Hylauronic Acid users have reported a positive side effect to using HA for wrinkle plumping is a noticeably more lush lash line. Worth a try anyway!
I’ve also tried a drop or two of some essentials oils that are known to encourage follicle growth, however they (being organic matter) allowed mold to grow so I do not recommend.
Editors Note: You can use oil-based products towards the very end of your lash extension cycle, where barely any extension are hanging on. As noted in our lash extension bible blog, you can (and should!) use lash growth serum on top of your extensions.