Definition: "The phantom smell may seem to always be there or it may come and go. Phantosmia may be caused by a head injury or upper respiratory infection. It can also be caused by aging, trauma, temporal lobe seizures, inflamed sinuses, brain tumors, certain medications and Parkinson's disease."
Anyway, I know it can be done by the unseen, because I've been subject to it while "hearing" the reasons. I've had good and bad smells. In metaphysics, they say the smell of flowers is angel communication, a deceased family member, or the presence of God. It stands to reason that there are those who may want to torment others by bad odors (that good and bad thing). But, you can receive guidance via the five senses. In the sense of smell, it’s called clairolfaction.
One of my most profound odor experiences, I wrote about in my book, Great Flame Within. I had been under a horrendous psychic attack and Jesus came to me to help. He put an odor under my nose of a cologne I wore back then called Obsession.
Now, I'm not promoting my book or the cologne, I'm just saying that, apparently, some things still seem to be outside our current scientists' awareness. Maybe we should be investigating or understanding that dimension,.
Because, as a South American Shaman once said: all illness is spirit, yours or another's.