Hello Nadine. I use both of them. But I don't know the exact ingredients and their quantity. But what I could imagine is that since the lash serum is designed for use on the eyelash line, i.e. around the eye, the ingredients might be milder/more tolerable than those of the Nanobrow serum. I don't know how Nanobrow affects the eye. Also, the applicator may be too thick for use around the eye. Nanolash has an extremely fine brush, Nanobrow does not.