Well, When I first got her, she went into her first heat and was a raging lunatic, nickering and squirting at anything that moved, including people! So, I started her on it and had her on it for a few months, and I barely noticed her heats after that. Then, I ran out of it, so I thought 'ok, we'll see if its actually doing anything before I buy more'. She went into heat and was again a lunatic, nickering and squirting at everything, totally distracted. So, I started her on it again and she's back to herself. I have no doubt about whether it works, it drastically makes a difference. And I'm such a cheapskate, it has to work really well in order for me to spend money on it!