This is a hard one to review as I've seen different results & reactions on different people. I actually used to sell this to clients through my beauty salon until they decided to pull it from salons & sell it in farmers & pharmacy stores.
I personally have pretty long & curly lashes so didn't try it until I saw the amazing results it had on one of my sisters. Hers ended up very very long & full. I had another sister who reacted to it having itchy & red lids so she gave me her left overs. After using it on me, all it basically did for me was slightly lengthen, full them out but made them super curly. And already having curly lashes they just ended up curling back over them selves looking like I had a lash perm gone wrong.
So it does work but it is very reactive. If you have sensitive eyes or skin I wouldn't recommend it.
I have been using this for months and have found it does wonders for my lashes. It has given my lashes a bit more volume and lots more length since using it. It took a few weeks for it to kick in but I stuck at it and started to get results. I still have to use mascara but when I do I get people asking if I'm wearing falsies. I have also used Revitalash but definitely prefer fLash, especially with the huge price difference!
Tips: I've made it last ages by putting a small bit on my finger and massaging it into my lash line. It recommends you use the little brush to apply it like eyeliner but I found that to be more than enough but when I use my finger its just right.