Iris Kulbatski in The Scientist:
Scent is a powerful time portal, reviving long-forgotten memories in stark detail. The human brain begins to build a library of smells in infancy, which grows into adulthood. For people with hereditary hyperosmia—a rare, heightened ability to detect and discern scents—this smell repository can be vast and remarkably fine-tuned. Joy Milne, a retired nurse, patient advocate, researcher, and grandmother, discovered this superpower as a child.1 Milne’s grandmother—also a super sniffer—trained her to identify scent signatures, as her own mother had taught her. As a nurse, Milne acquired an extensive clinical scent library, recognizing patterns between disease symptoms and diagnoses. After her late husband’s Parkinson’s disease (PD) diagnosis, she realized that the musky smell he wore at the nape of his neck for over a decade was an early warning sign and that she could detect it in other PD patients.
More here.