This is the first eyelash serum I have ever tried and I am very impressed! In two weeks I have seen an improvement in the thickness and length of the lashes, and now after six weeks I am obsessed. I also use it on my brows and now they are much thicker too. Even with religious daily use, I only used about 1/6 of a bottle so I'm very happy with how long it will last. I also have very sensitive eyes, and this was not at all irritating.