is it like the DAP diffuser? (Dog appeasing Pheromones? just googled and it seems they are pretty much the same).
If so I used it for separation anxiety when Lucky was younger. I did a bunch of things though ... from having a kong dispenser give him treat filled kongs randomly throughout the day, to special dog music, to a diffuser, to spraying his bedding with DAP and even rescue remedy on a treat before I left ... No idea what REALLY worked, but he got better and now we keep the music but that is all. Apparently it is studied to make a difference. It is pricey though! I'm not 100% sure, but it may be worth a try if you are not having luck with other things.
Have you looked at Thundershirts? I know people who absolutely swear by them.
they are pricey too, but you'll have them forever.
(a.k.a. Lucky's & Sparky's mom!)