Got BO? Blame the bacteria living in your armpits. In some people, bacteria cause body odour that no deodorant can disguise. But replacing them with underarm bacteria from a less smelly person can solve the problem, for a month or two at least.
Our bodies are crawling with bacteria that have evolved with us and can affect our health. Disrupting the bacteria in our gut, for example has been linked to all kinds of intestinal, immune and brain disorders.
The skin has its own microbiome too, and it varies by region – there can even be a difference between the bacterial ecosystem of your left and right armpits. The bacteria that live there probably have a role in producing the volatile compounds that give sweat its smell, says Chris Callewaert at the University of California, San Diego.
A few years ago, Callewaert met a pair of identical twins – one of whom had particularly bad body odour. Callewaert suspected that the collection of bacteria living in the twins’ armpits might be responsible for their different personal scents. To find out, he swapped out the stinky twin’s armpit bacteria with that taken from his twin brother.
Callewaert first asked the twin that didn’t smell to refrain from washing for four days. This is because the bacteria in our armpits live deep in the skin, so it takes a few days for them to be shed to the surface with dead skin.
Meanwhile, the stinky twin scrubbed his pits with antibacterial soap every day, for four days. The idea was to remove as much of his armpit bacteria as possible, creating a clean state for his brother’s microbes.
When Callewaert collected the nicer-smelling twin’s dead skin – which was loaded with his bacteria – and swabbed it in the armpits of the smellier twin, the man’s body odour problem rapidly disappeared. “The effects have persisted for over a year now,” says Callewaert. “We’re very happy with that.
Callewaert and his colleagues have since repeated this procedure with 17 other pairs. In each case, one person in the pair had a body odour problem, and the other person was a close relative who was willing to donate bacteria from their armpit microbiome.
Before and after the bacterial transplants, the offensiveness of the previously smelly people was judged by a “trained odour panel” of eight people, says Callewaert.
Out of the 18 pairs, 16 saw improvements in body odour within a month. Half of the group had long-term improvements that lasted three months or more. Callewaert presented the results at the Karolinska Dermatology Symposium in Stockholm, Sweden, last month.
“It’s very cool, and the idea is sound,” says Emma Allen-Vercoe at the University of Guelph in Ontario, Canada. “Some people suffer with body odour that’s really overwhelming,” she says. “Maybe the answer is to replace their microbes with ones that aren’t producing such volatile compounds.” She hopes that a similar approach might be useful in treating some skin conditions, like eczema and psoriasis.
Callewaert and his colleagues are now formulating a more general brew of bacteria that could be used in place of a relative’s armpit scratchings. “It’s still very experimental, but I’m sure it can work,” he says.
Until this is available, there are other ways you can improve your body odour bacteria. Microbes that feed on lipids – compounds that include fats and oils – are especially bad for body odour. You can try limiting the amount of lipids in your skin by keeping a healthy weight and avoiding fatty foods, says Callewaert. “People that eat fast food and meat smell worse, while those that eat vegetables smell better,” he says.
Shaving can also help, as can wearing the right clothing. When we wear clothes, we transfer bacteria to them, and some fabrics encourage the growth of “bad” bacteria associated with offensive smells. Washing your clothes doesn’t solve the problem, either – it merely helps spread the bacteria among the contents of your washing machine. Polyester seems to be particularly bad, and is one to avoid, says Callewaert.