The investigators collected t-shirts from 26 healthy individuals following an intensive, hour-long bicycle spinning session, and incubated the shirts for 28 hours before having them inspected by a trained odour panel.
The researchers also investigated the taxonomy of the bacteria on the shirts, and in the axillaries.
Freshly secreted sweat has little odour, because the long-chain fatty acids the axillaries secrete are too big to be volatile, said first author, Chris Callewaert of Ghent University, Belgium.
Bacteria break these, as well as hormones and sulphur compounds, down to waftable sized, odouriferous molecules.
On the clothes, the main culprit bacteria are micrococci, said Callewaert.
"They are known for their enzymatic potential to transform long-chain fatty acids, hormones, and amino acids into smaller volatile compounds, which have a typical malodour," Callewaert said.
Staphylococci, which inhabit both axillary skin and adjacent textiles (the latter with much less diversity), create a normal, non-malodorous body odour, he said.

"The micrococci are able to grow better on polyester," said Callewaert.

Corynebacteria are the main causes of bad odours in the armpits, but these anaerobes fail to grow on textiles, said Callewaert.
The impetus for this research is the suffering caused by unpleasant body odour (BO), said Callewaert.
"BO is taboo, and its prevalence is greatly underestimated," he said.
"There is little these people can do to help themselves. Some of them are too psychologically distressed to talk to strangers, or even to leave the house, afraid of what people might think of their smell," said Callewaert.
The study appears in the journal Applied and Environmental Microbiology.

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