25-09 - Flipbook - Page 136
Mi n i str i es
People with liver disease can emit a musty or sulphurous odour from their breath or urine, while if
your breath smells of ammonia or has a "fishy" or
"urine-like" aroma to it, then this could be a sign of
kidney disease.
Some infectious diseases also give off characteristic smells. Sweet-smelling poo could be a sign of
infection with cholera or the Clostridioides difficile
bacteria, which is a common cause of diarrhoea 3
although one study found a group of unfortunate
hospital nurses were unable to accurately diagnose patients by sniffing their faeces. Tuberculosis,
meanwhile, can cause a person's breath to smell
foul, like stale beer, and their skin like wet brown
cardboard and brine.
Detecting other diseases, however, requires a special kind of nose.
Dogs, for example, have a sense of smell that is reportedly up to 100,000 times stronger
than ours. Scientists have trained canines to sniff out lung, breast, ovarian, bladder, and
prostate cancers in people. In one study on prostate cancer, for example, dogs were able
to detect the disease in urine samples with a 99% success rate. Dogs have also been
trained to detect early signs of Parkinson's disease, diabetes, oncoming epileptic seizures,
and malaria, all from smell alone.
But not all dogs have what it takes to become a disease detector, and it takes time to train
the animals that do. Some scientists say we can replicate the amazing olfactory capabilities of canines, and people like Milne, in the laboratory, perhaps offer the chance to have
a simple swab that could be sent off for testing.
Barran, for example, is using gas chromatography-mass spectrometry to analyse sebum (an
oily substance produced on people's skin) from Parkinson's patients. Gas chromatography
separates the compounds, and mass spectrometry weighs them, allowing you to determine the precise nature of the molecules present. The food, drink and perfume industries
already use this form of odour analysis routinely.
Out of the 25,000 or so compounds commonly found on human skin, roughly 3,000 are differently regulated in people with Parkinson's, says Barran. "We are now in a position where
we've narrowed that down to about 30 that are really, really consistently different in all
people with Parkinson's."
A lot of the compounds are lipids, or fats, and long chain fatty acids, she says. For example,
one early study focused on three lipid-like molecules linked to the odour caused by the disease 3 hippuric acid, eicosane and octadecanal. This makes sense as previous studies suggest that abnormal lipid metabolism is a hallmark of Parkinson's disease.
