Has the opposite effect!
I’ve had Feliway in the past and it seemed to help my cat through stressful situations such as building works, but the latest order smelt different (previously I could never smell it). Within minutes of it being plugged in, my cat was stressed, pacing, growling, spraying outside of the litter box and seemingly looking everywhere for the intruder. As soon as I turned it off, she started to settle.