Bought this to try to help one of our cats to feel more relaxed. We have two cats at home and the Feliway definitely had effects on them. One, Niko, usually hassled for food and meows all the time and the other, Bella, is shy. We set up the diffuser and Niko was more relaxed and there was less hassling, meanwhile Bella was more friendly and played in the house more often (which she rarely does). However, after a week or so, Niko had an episode where he was struggling to move around and kept howling whenever we tried to pick him up. He's been diagnosed with feline asthma previously and my boyfriend was thinking that the Feliway is not too good for his breathing. We had to go to the vet ER and met with a specialist the next day who advised us to unplug the diffuser as it might be the trigger to his asthmatic attack. We unplugged it straight away and he's been recovering good since.
All in all, this product works, although not for all cats. If your cat has asthma or other respiratory diseases, I don't recommend this product to be used at your home or at least see your vet and ask for their opinion first.