There are warnings about using essential oils around cats. Melissa Shelton, author of the Animal Desk Reference, writes from her personal experience on pages 321-322:
"After hearing all of the concerns and warnings from the veterinary community, I had concerns for my own multi-cat household. Routine blood and urine evaluations calmed the concerns, and no detrimental effects have ever been shown with over 3 years of almost constant diffusion in my home. What I eventually found to be true, was that veterinarians who were so carefully warning other veterinarians and owners not to use essential oils, had in fact, never used them themselves. The oils that were linked to killing cats and harming animals were also never graded or evaluated by veterinarians who condemned them."
"My current recommendation when considering essential oil use for cats is to choose oils that are used often, have been used in many cats, and to use them with techniques that cats enjoy."
"One factor that is true for cats, is that they are notoriously deficient in the Cytochrome p450 liver metabolism pathway. This particular pathway is utilized for the metabolism and excretion of all sorts of chemicals from their body, including traditional medications. A cat's liver just does not metabolize items in the same manner or efficiency as a large dog or a human. This fact has made cats unique in veterinary medicine, no matter what the substance may be that we are exposing them to. For example, certain traditional Non-Steroidal Anti-Inflammatory (NSAID) drugs can be used in dogs, but if given to a cat, has a high likelihood of causing significant damage to organs and even death."
Water Diffusion
(from the Animal Desk Reference by Melissa Shelton, DVM, page 323)
Diffusion is usually a method that is well tolerated by all cats, especially from water-based "ultrasonic" diffuser models. Many misconceptions have been placed on what cats 'like' or 'don't like' - and it appears that these generalizations may have been based on individual reports, and not from cats as a whole. The dislike of citrus oils may hold true for one cat, but then another cat is found to be attracted to the diffusion of [Peaceful blend]. Allowing a cat to show you their individual preference is a good idea. If a cat can leave the room when you diffuse a certain essential oil, you will quickly find out if they tend to enter a room every time a certain essential oil is used."
Litteroma
(from the Animal Desk Reference by Melissa Shelton, DVM, page 331)
Use unscented litter. Add 1-3 drops of chosen essential oil (Copaiba for arthritis) to 1 cup baking soda, and store this mixture in a glass jar, allowing it to "marinade" overnight. Shake the mixture several times. You can add more essential oils if desired. Sprinkle a small portion onto the kitty litter and mix well. Provide a second litter box without the essential oil to make sure that your cat does not have an aversion to the essential oil selected. Once you are sure your cat is using the litter box with your essential oil selection and concentration, you can then omit the use of the "plain" litter box. Shelton mentions that people add Copaiba for arthritic issues, Digestion Support for intestinal upset and Frankincense for cancer.
Kitty Raindrop Technique
(from the Animal Desk Reference by Melissa Shelton, DVM), pages 325-326
"Although this technique included oils that are typically contraindicated in cats, veterinarians and cat owners alike have witnessed amazing health benefits with this technique. Because of its formulation specifically for cats, it is remarkable to watch cats enjoy this application so much. I have documented the safe and even long term use of the Kitty Raindrop Technique (KRDT) in many cats with blood work and veterinary monitoring. One such case study is of a cat named "Cowboy" who has received a KRDT daily to twice a day for over 2 years!"
Add 4 drops of each oil to a 30ml bottle with dropper orifice:
[HEO's comment: We make a blend of these oils called "Raindrops"]
Apply 6 drops up the spine of the cat, from tail to head.
Gently stroke or feather the essential oil solution up the back of the cat. Cat's often enjoy this backward stroke, but if not, pet the other direction.
Modification of KRDT:
When modification of the KRDT is suggested, this is generally referring to the addition of essential oil(s). In general 4 drops of the additional oil are added to the existing recipe, unless less is specified for that individual oil. On average, no more than 3 essential oil singles or blends are added to a KRDT solution.