How dogs can detect Parkinson’s disease

What if some of the best medical detectives didn’t wear white coats or carry stethoscopes, but instead had wet noses and wagging tails? Across hospitals and research labs, scientists are uncovering just how extraordinary a dog’s sense of smell can be, and how it might change the way we detect disease.

A study published in the Journal of Parkinson’s Disease has shown that specially trained dogs can detect the scent of Parkinson’s disease with impressive accuracy. Led by Dr. Nicola Rooney of the Bristol Veterinary School and Medical Detection Dogs in Milton Keynes, the research involved a collaboration between veterinary experts, chemists, neurologists, and even a woman known as a “super smeller.” Their collective effort has brought us one step closer to a non-invasive, early detection tool for a disease that affects more than 10 million people worldwide.

Why is Parkinson’s so hard to diagnose?

Parkinson’s disease (PD) is best known for its motor symptoms, including tremors, stiffness, and slowness of movement. But those signs often appear only after years of underlying damage to the nervous system. By the time a patient receives a formal diagnosis, significant loss of dopamine-producing brain cells has usually already occurred.

Doctors today don’t have a simple, definitive test for Parkinson’s. Instead, they rely on a combination of neurological exams, patient histories, and sometimes costly brain scans. This creates delays in diagnosis, and for a progressive condition like Parkinson’s, those lost years matter. Earlier diagnosis could mean earlier treatment, better management of symptoms, and perhaps, in the future, slowing the disease’s progression.

So where do dogs come in?

Dogs live in a world of scent. While we humans have around 5 million scent receptors in our noses, dogs boast up to 300 million. They can detect odors at concentrations nearly 100 million times lower than we can. That’s why dogs have been successfully trained to detect everything from explosives at airports to early-stage cancers, diabetes-related blood sugar changes, and even malaria.

And then there’s sebum. Sebum is the waxy, oily substance our skin produces. For reasons scientists don’t yet fully understand, people with Parkinson’s tend to produce more of it, and it has a distinctive odor. Some patients notice it, but one woman in particular, Joy Milne, has become famous for her extraordinary ability to smell Parkinson’s. Joy’s husband developed the disease, and she noticed his scent had changed years before doctors confirmed the diagnosis. Her gift sparked research into whether Parkinson’s really does leave a detectable “odor signature.”

Turns out, it does! And dogs are the perfect partners to prove it.

Inside the study: dogs as disease detectors

Dr. Rooney and her colleagues, including chemists like Professor Perdita Barran from the University of Manchester and neurologists such as Dr. Monty Silverdale at Salford Royal Foundation Trust, rigorously tested whether trained dogs could tell Parkinson’s patients apart from healthy individuals using only their noses. First, they collected samples. Volunteers with Parkinson’s and healthy control participants provided skin swabs. Importantly, the samples from patients were drug-naïve, meaning the individuals had not yet started Parkinson’s medication. This helped ensure that any scent difference came from the disease itself, not from treatment. Then, they trained the dogs. Ten dogs were initially screened. Of those, five showed promise, and after months of training, two proved particularly skilled: a two-year-old golden retriever and a three-year-old Labrador–retriever mix. Finally, they put everything to test. After 38–53 weeks of training, the dogs faced their toughest challenge: a double-blind trial where neither the trainers nor the researchers knew which swabs came from Parkinson’s patients. Each dog was presented with 100 new samples, 40 from people with Parkinson’s and 60 from controls.

The results? The golden retriever detected Parkinson’s correctly in 70% of cases, while the Labrador–retriever mix scored 80%. Just as importantly, their accuracy in ignoring the healthy controls was even higher: 90% and 98%. In other words, the dogs weren’t just guessing, they were consistently identifying a genuine scent marker linked to the disease.

While a dog in every clinic isn’t the likely future of Parkinson’s diagnosis, the study’s implications are powerful. It shows that there is indeed a detectable odor signature of Parkinson’s disease, and that opens the door to developing laboratory-based tests.

Think of the dogs as living proof-of-concept machines. If a golden retriever can sniff out the disease, then scientists should be able to identify the chemical compounds responsible and build devices or “electronic noses" that replicate the same feat.

In fact, researchers are already analyzing the molecular makeup of sebum to pinpoint the biomarkers that give Parkinson’s its unique scent. Pairing this chemistry with the canine studies provides a double validation: both dogs and machines can detect the disease, making future tests more robust.

The study raises as many questions as it answers. Could dogs detect Parkinson’s even before patients notice symptoms? Could electronic noses trained on the same sebum samples become cheap, portable diagnostic tools in clinics worldwide? Might similar methods reveal scent markers for other neurological diseases?

Long-term studies are already underway to see whether dogs can pick up on Parkinson’s even years before diagnosis. If so, it could revolutionize screening and allow patients to begin therapies earlier. And beyond Parkinson’s, this research strengthens the idea that our bodies broadcast subtle chemical signals when disease takes hold. We may not smell them, but dogs do, and soon, so might machines.

If you want to learn more, read the original article titled "Trained dogs can detect the odor of Parkinson's disease" on Journal of Parkinson’s Disease at https://doi.org/10.1177/1877718X251342485.