I made the mistake of taking a nasal flu “shot.” I went through about three months of olfactory hallucinations (smelling things which weren’t there) and wound up going through an MRI looking for a brain tumor. Nothing there. I lost my sense of smell at month four and haven’t had it back in thirteen years. I get whiffs of stuff about two or three times a month, but it doesn’t stay.
I lost my sense of smell after sinus surgery back in 2008, and the doc said I might never get it back, but slowly it has returned, but not 100%.........................