I've tried this on both my cats at varying times of stress. It wasn't just a once-off as I wanted to see whether it may work in some situations but not in others. But it made no difference at any time.
I love Bach Remedies in general and would recommend them all the time. But just like I would tell my people patients I tell animal owners, it will work on some and not on others. They're natural flower extracts and it just depends on the persons/animals body. We don't all respond the same way.
I found using the Beech Bach Remedy worked better than the Rescue Remedy for my cat when introducing our new kitten. The Beech Remedy is to help with your pets confidence.
I would add it to my cats water bowl or put a few drops on his favorite treat.
Here's what I wrote about my experiences with calming aids
1. I know a lot of people use feliway (expensive and didn't work on my cat) but I use natures miracle calming spray (Cheapest on amazon) and he loves it.
2. For stressful situations I use Bach Remedies. They have a few different remedies that they recommend for animals. I've used Rescue Remedy for pets which I've used for general stress situations, and I've used Beech for his confidence because he's fearful of new things.
When I brought home a kitten for my cat to have as a companion I added drops of Beech to his water to make things less stressful. I don't know if this is the reason their introduction went so well and that they love each other, but I know it definitely helped. I kept adding drops to my cats water for the first 2 weeks or so until I saw that they were sleeping together and that they loved one another. It really does make a big difference so just take note that when you give it to your friend that they're going to act different. My very active, playful, energetic cat became subdued, sleepy and calm. That being said, it's only temporary. Once you stop giving the drops I find that within a couple of days they return to being themselves but without any stress.
I'm not a vet and I'm only giving advice for what I've personally used with my cat and that's helped me. There's plenty of information about Bach Remedies for pets online for you to read about.
That being said I believe it's worth the $ to try it.
I've used this before on my cats and I think it works. The first cat was a feral I was trying to tame and bring in to get used to the house. She was letting us handle her outside, but we had other cats in the house. Kept her separated from them and had her in the house for 3 days on Rescue Remedy but she was always wanting out. Started to get a little nasty with us so decided to let her be an indoor/outdoor cat. Another elderly cat has been extremely needy (dementia starting?) and more vocal than usual, also has CKD. Trying to just keep her comfortable. Gave her some of this for a few days in a row and it has calmed her down tremendously...I think it works, but it's not miracle stuff.