Since I have two older cats, I wanted to make sure that diffusing essential oils was safe for them since there are some oils that are toxic to cats. I only diffuse the Young Living blends at home: Sleepyize, RC, and Peace & Calming at night in our bedroom. I do not use any oils directly on my cats, but they would be exposed to the diffuser and the Thieves household cleaning products.
The two major components that can affect cats are monoterpene hydrocarbons, which are in some citrus oils and some coniferous plants like pine and fir and high-phenol oils such as Cinnamon, Clove, Thyme, Oregano, Savory. Certain oils can affect their kidney and/or liver functions because they lack an enzyme that other animals have. It is recommended that you do not diffuse oils that are toxic to cats. Also wash your hands after applying oils to yourself before you pet you cats.
Some essential oils producers will dilute their oils with synthetics and/or additives to bring down the retail cost of the oil - that is why many of the store-bought oils are so cheap. The synthetics and additives used in store-bought oils can be toxic to cats. This is why I use Young Living's Essential Oils because they do not dilute their oils or use synthetics or additives. A fellow person in our essential oils group checked with their vet and they said that Young Living are the only safe oils to use around cats. That said, some should never be applied topically like Peppermint and Tea Tree oils.
I found this list on http://theessentialgirl.com Since there are a lot of proprietary blends, it is important to know each oil that is in a blend as they may contain some of these oils listed below.
I contacted Young Living's Product Support for further clarification and details and this was what they had to say about the matter. First, Thieves Household Cleaner is safe for use around children and pets.
Essential oils can be safely and effectively shared with your animal friends. Young Living’s products are intended only for the use listed on individual labels—either for topical/aromatic use or as a dietary supplement. Please always refer to the label for usage directions. For more information on how to utilize the Young Living® products for your animals, please visit https://www.youngliving.com/blog/essential-oils-and-pets-a-quick-how-to/. Diffusing: As every animal is different we would suggest diffusing small amounts for short periods of time (5 minutes every 1-3 times daily) and observing how the animal responds before increasing the amount and time. Special caution should be exercised when using essential oils with cats. Cats are also generally averse to citrus essential oils and high-phenol oils below. 1. Cinnamon Bark 2. Clove 3. Mountain Savory 4. Oregano 5. Plectranthus Oregano 6. Thyme
If you have further concerns, it is recommend that you seek the advice and recommendation of a competent, trained veterinarian with knowledge and experience with essential oils use on animals.