I don’t generally recommend the use of essential oils on dogs or cats. Dogs and cats have extraordinarily sensitive noses. It’s estimated that a dog’s sense of smell is between 100,000 and a million times more sensitive than a human’s.
Considering that, the use of an essential oil on a dog or cat would be similar to firing an air horn right next to your ear. Not pleasant.
Tea tree oil (Melaleuca) is toxic to dogs, particularly small dogs. Be careful.
Herbs on the other hand (with a few notable exceptions) can be used safely in dogs and cats. Most dogs will readily eat herbs mixed with a bit of canned food or baby food. Cats can be more of a challenge as one might guess. 😉
Doc
Don't use herbs or combine herbs with medications or use them during lactation or pregnancy without talking with your healthcare provider.