I have been busy writing the final book in my Healer’s Shadow trilogy. The heroine, Judith, is a traditional healer as well as a perfume maker. She therefore has a very refined sense of smell, which she uses to diagnose disease. You might suggest that this ability is part of the novel's magic realism, but there is some evidence that cats and dogs can detect illness in their owners and modern-day researchers are looking at developing an “electronic nose”, but in the past healers, like Judith, would have used their own sense of smell.
When I was researching the book in the Bodleian Library in Oxford, I found a fascinating old book, which listed the smells of different illnesses. In traditional medicines healers and doctors would smell the urine, breath and skin of the patient. The book listed some of the smells of different diseases.