So this does NOT reverse grey hair. This is false advertising and sleezy if you ask me. It slowly dyes your hair over time AND everything it gets on, including my bed pillows, couch pillows, shower curtain, tub, bathroom floor, etc. I didn't realize how easily it rubs off onto EVERYTHING. So that's been a bit of a pain. It also does not wash off your hands as easily as they say. Also, eventually the top of your hair becomes a darker color than the bottom because of the continual dying. It only took a little over a week for this to happen on my hair and it looks ridiculous. Some of the greys turned this weird copper color. Having said that, I gave it 2 stars because it does cover the greys quickly and I've decided to use it in just small spots where I have the most greys, but sparingly. I'm thinking I might be better off having it dyed by a professional though so that the top isn't darker than the bottom. I'm not sure I understand the raving positive reviews, but glad others had better experiences than I did.