Some cats do have a better ability to metabolise essential oils and other aromatics than others and as I work professionally as an Animal Essential Oil therapist, I do come accross cats who are absolute oil junkies but I still only work according to the individual response. I was teaching an Owner/Carer workshop the other day and one of my cats came flying in and almost dived into the bottle of Rose Absolute yet the others sometimes won't come into the room when I have my oils out. It also has to be said that there is a potential game of Russian Roulette going on with some cats and you could reach a level of toxicity after a while that will only be apparent when the cat goes into liver failure so it is impossible to give a "safe" threshold for working with cats.
This is also an issue if you use oils in the cats usual environment so if you use a spray to deter cats from scratching etc, make sure you well ventillate the room after the point has been made. Many cats will just avoid the area altogether till the aroma has dissipated but in general I would be VERY cautious of using essential oil sprays with elderly, ill or young cats.
As Binah has already suggested, Hydrolats are a better bet but remember too that their chemistry differs from that of the corresponding oil due to the presence of heavy and water-soluble molecules so you need to take the properties of the complete herb into account when deciding which to use. 2-3 drops in a saucer of water, changed daily (and placed well away from their usual drinking water in case the aroma stops them from going to drink) is usually well accepted by cats of all ages who will then self-medicate according to need.
Hope this is useful info.