Japanese culture has a specific term for the distinct musty odor that often accompanies aging bodies – kareishu or “old people smell.” As people grow older, their body chemistry changes, which leads to a change in their personal aroma regardless of hygiene practices. This phenomenon is so well-known that the Japanese came up with a term to describe this common aspect of aging.
Kareishu comes from a buildup of 2-nonenal, a chemical compound that increases naturally in the body as we grow old. The origins of the smell can be traced to the sebaceous glands in skin, which produce more 2-nonenal over time. Even fastidious elderly people cannot wash away kareishu—it’s an integral part of the aging process.
So what does kareishu actually smell like? Many describe it as musty, stale, grassy or waxy. It conjures up scents found in old books and newspapers. To the Japanese, kareishu smells like an old person’s home, triggering nostalgic memories of grandparents’ houses.
Distinct Odor of Parkinson’s Disease
Kareishu may be a normal sign of aging, but scientists are discovering that specific odors can also be indicative of certain diseases. Smells emanating from human breath, skin and bodily fluids offer clues into medical conditions brewing inside.
Dogs have already proven adept at sniffing out cancer and other ailments from human odor alone. One woman with an extraordinarily acute sense of smell is showing the same ability. Meet Joy Milne, a Scottish woman who can smell Parkinson’s disease years before symptoms even arise.
Milne first detected a distinct odor on her husband Les nearly a decade before he was diagnosed with Parkinson’s at age 45. She describes the early scent as intensifying over the years into a yeasty, greasy and metallic smell that reminded her of nursing homes.
After attending a Parkinson’s support group meeting years later, Milne had an epiphany – the musky odor she smelled on her husband was present on the other people with Parkinson’s there as well. She could discern different stages of the disease based on scent alone. Milne brought her observation to scientists, who devised an experiment confirming her incredible ability.
By sniffing the worn t-shirts of study participants, Milne identified those with Parkinson’s with incredible accuracy. She even flagged a supposedly healthy man as having the disease months before his diagnosis. Clearly, Milne could detect Parkinson’s in the earliest stages by scent.
Her supernatural sniffer has since pinpointed those with other conditions like Alzheimer’s, tuberculosis and cancer as well. Thanks to Milne’s keen nose, researchers now know that distinct biomarkers exist in skin secretions well before diagnoses occur.
Milne’s gift is unlocking mysteries about the pre-clinical phases of diseases. Identifying those markers early on can revolutionize diagnosis and treatment down the line. One day, a simple skin swab could let doctors screen for impending Parkinson’s years ahead of time when prevention measures work best.
They may seem completely unrelated, but the unique odors of kareishu and certain diseases both offer insight into the chemicals at work inside our changing bodies. Kareishu represents aging while the scent Milne recognizes signals Parkinson’s specifically. Her nose is leading science to non-invasive early detection techniques that can save lives.
Who knew the most unassuming human sense could have so much to teach us? Research continues on decoding the olfactory markers that may one day predict vulnerability to complex, devastating illnesses. The inspiring work of Milne and scientists confirms there is much left to understand about how smells reflect our health – both in aging and disease.