Essential oils are to be used with caution. For instance, for a 70kg man, 3 to 4 drops of essential oils are usually recommended. For a cat, the equivalent dose corresponds to half a drop, obviously making it very hard to dose! That is why it is best to use inhalation mixes made specially for cats. This allows you to dose correctly and to be certain that you are only using essential oils that are harmless to your cat when inhaled! Furthermore, certain essential oils are more efficient when combined.
You can find in inhalation mixes made for man some essential oils that are not recommended for cats:
If despite all of these precautions your cat our yourself (or a child or an asthmatic individual present at the time of inhalation) displays a single side effect, you should immediately stop all use.