The thought of being diagnosed with Parkinson’s disease strikes fear into the minds of all but the most stoic individuals; early detection is difficult, and it is currently an incurable condition. So it is quite astonishing that Joy Milne, a 65-year-old woman, has the ability to “smell” the disease in people, as reported by BBC News. She first noticed the scent on her husband – which she described as a very subtle, musky smell – six years before he was given a medical diagnosis of Parkinson’s disease.

She only made the connection after she joined the charity Parkinson’s U.K. and met with other sufferers of the disease, each with the same odor. This led researchers at the University of Manchester to test her out in a controlled, laboratory setting; they found she could very accurately identify people suffering from the disease by smelling the t-shirts they slept in.

It is thought that the sebum – an oily fluid that lubricates and waterproofs the skin – is chemically altered in those suffering from Parkinson’s, producing a unique chemical that can only be detected by those with incredibly powerful senses of smell, including Mrs. Milne.

Parkinson’s disease is a slow, progressive neurological disorder that damages specific nerve cells within the substantia nigra, the part of the human brain associated with risk, reward and movement. It is a truly debilitating disease, rendering a person unable to control tremors in their otherwise stiff and inflexible muscles. Nerve cells that produce dopamine – a molecule that helps to coordinate movement in the muscles – are severely damaged. 

Both humans and dogs, along with most mammals, have scent glands. Information about a member of another species can be ascertained either consciously or subliminally by inhaling scents, such as sexual intent, mood, social status and health.

Dogs have at least 220 million scent glands, so it may be remarkable, but not surprising, that they can smell the chemicals given off by cancerous tumors in humans. Cancerous cells produce these chemicals (“volatiles”), which are then removed from the body through urination. Dogs – with some training – can pick up on the odor of these volatiles in urine samples and react to their presence.

However, it’s extremely unusual that a human, which typically has only 5 million scent glands, can detect the volatiles being emitted from someone afflicted with Parkinson’s. This has convinced the University of Manchester, along with Parkinson’s U.K., to start a new study analyzing the unique volatiles produced in the sebum of sufferers.