Diagnosis remains the cornerstone of effective treatment and prognosis. From ancient manuscripts like the 1600 B.C. Edwin Smith papyrus to the 1000s B.C. Babylonian Sakikkū tablet, early physicians relied on touch, sound, and even the sense of smell to detect disease. The Middle Ages saw uroscopy, a ritual that examined urine visually, chemically, and olfactorily.
With the scientific revolutions of the 18th century, the six human senses were largely set aside in favor of laboratory tests and imaging. Yet the possibility that the human nose could still detect disease persisted—and modern research is beginning to confirm it.
In 2009, Joy Milne noticed a persistent “nasty yeast” odor emanating from her husband. Despite thorough cleaning, the smell lingered. In 2013, at age 45, her husband was diagnosed with Parkinson’s disease, a neurological disorder typically identified only after motor symptoms appear.
When the Milnes attended a Parkinson’s support group, Joy immediately recognized the same pungent scent she had been smelling for years. She and her husband, a medical doctor, suspected she might have identified Parkinson’s before symptoms manifested. They approached Dr. Tilo Kunath, a neurologist who initially dismissed the claim.
Inspired by cancer‑sniffing dogs, Dr. Kunath designed a blinded test. Joy sampled overnight t‑shirts worn by Parkinson’s patients and healthy controls. She correctly identified all Parkinson’s samples and misidentified only one control. Within a year, that subject was also diagnosed with Parkinson’s, validating her sensitivity.
Olfaction relies on millions of olfactory receptor neurons in the nasal epithelium. Each of the ~500 receptor types binds specific volatile molecules, and the pattern of activated receptors creates the perceived scent. When a person’s body chemistry changes, so does the profile of emitted molecules.
Milne and Dr. Kunath isolated the chemical signature of Parkinson’s from patients’ sebum—a skin‑secreted oily layer. They identified two key compounds: perillic aldehyde and eicosane. The combination of these molecules reproduced the odor Joy described, confirming that Parkinson’s has a distinct scent.
Their study, published in ACS Central Science (2019), was a landmark in olfactory diagnostics. Though no routine test exists yet, the discovery opens avenues for early, non‑invasive screening.
Joy Milne continues to collaborate with researchers, demonstrating that the human nose, paired with modern analytical tools, can play a pivotal role in disease detection.
