The short answer is ‘It Depends’. The long answer (isn’t there always a long answer?) is, it depends on what you are expecting the oils to do.
Dogs have a very acute sense of smell and essential oils basically work with smell.
On the other hand, essential oils wouldn’t do much for cancer, a broken bone on an infection.
A lot of people ask me ‘Doc, I don’t like the idea of giving my dog all those chemicals and pills, so can I just use massage, herbs and aromatherapy instead?’
And I always answer ‘Massage and aromatherapy are a great idea but since your dog has a cancer/broken bone/infection/endocrine disease/kidney failure/….(insert the name of your dog’s serious illness here) I just don’t think a bit of herbs are going to fix it. So aromatherapy or not, you will still need to buy those pills and pay for that $2,000 surgery.’
By the way, Lavender oil for dogs is my favourite. There is evidence that if diffused through the air, it reduces anxiety and helps with motion sickness. But it’s unproven against brain tumours. You can try, of course but don’t blame me if it doesn’t work.