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12

Lab Times

1-2015

Opinion

H

umans are smelly animals! We naturally produce a

range of odours that we try to wash off or disguise. Yet

some people truly suffer from their smell and need sci-

entific help. At least, this is the avowed goal of Chris Callewaert

– self-proclaimed ‘Doctor Armpit’ – whose mission at Belgium’s

Ghent University is to understand and regulate armpit odours.

On his ‘Dr Armpit’ website –

www.drarmpit.com

– Calle-

waert brings hope to the odour-challenged, with reassuring

messages like “Remember: if you have a body odour, it is not

your mistake: it is the mistake of your bacteria.”

His research focuses on “malodor-generating bacteria” and

how to counteract them in armpits, clothes, washing machines,

etc. Recent studies include the formulation of ‘synthetic sweat’

(

J Microbiol Meths

, 103:6-8). Apparently, this concoction per-

mits all armpit bacteria to grow as they

would on armpit skin: “Even the formed

odour and malodor molecules resemble

the original odours.”

Solutions for “the malodor generation”

In his latest research article – the “Mi-

crobial odour profile of polyester and cot-

ton clothes after a fitness session” – Calle-

waert claims to be on the verge of revolu-

tionising textiles (

Appl Environ Microbiol

,

80(21):6611-9). Using his findings, “the

textile industry can design adjusted cloth-

ing fabrics which promote a non-odour

causing microbiome”.

Human armpits (axillae) can contain

10

7

bacteria per cm

2

from up to nine differ-

ent phyla. Or as Callewaert told the

Wash-

ington Post

(13/08/14), “A lot of bacte-

ria reside in our armpits. In fact, there are

more bacteria in your armpits than there

are humans on this planet. So you should

never feel alone!”

Our body odour is determined by specific bacterial species.

Although freshly secreted sweat has little odour, bacteria sub-

sequently break down long-chain fatty acids, hormones and

sulphur compounds to smaller odoriferous molecules.

Our clothing helps create a warm, moist environment on

the skin that provides further potential for bacterial growth

and the generation of unpleasant odours. To study how differ-

ent textiles affect these odours, Callewaert asked volunteers to

get hot and sweaty and then smelled their T-shirts.

Role of clothes in odour generation

Twenty-six healthy subjects, wearing freshly-washed cot-

ton, polyester and mixed fibre T-shirts, participated in an inten-

sive one hour session of bicycle spinning. Their sweaty T-shirts

were subsequently collected, placed in plastic bags and incu-

bated for 28 hours in the dark at room temperature. This “sim-

ulated the home conditions” and let the microbial community

grow on the specific clothing textiles.

The individual T-shirts in the plastic bags were presented to

a panel of seven “selected and screened human assessors” who

sniffed them for their odour characteristics. The trained odour-

smelling panel found that sweaty polyester smelled worse than

sweaty cotton. Not only did the polyester T-shirts smell less

pleasant, their odour was also found to be more intense, musty,

pungent of ammonia, strong, sweaty and sour.

Looking at Callewaert’s methods section, however, some

anomalies emerge. For example, why were the odour-testers

only presented with a clean cotton T-shirt as their “blank odour

measurement” and not a control polyester T-shirt? And why,

in addition to testing ten cotton and ten polyester T-shirts, are

there six with mixed fibres: four with 95%

cotton/5% elastane, one with 82% polyes-

ter/18% elastane, and one of 35% polyes-

ter/34% cotton/28% lyocell/3% elastane?

The answer would appear to be that all

26 participants used their own T-shirts. This

would also explain why Callewaert said he

had to test complete T-shirts when “incubat-

ing” them for bacterial growth – he couldn’t

simply cut-up his participants’ T-shirts to iso-

late the “armpit” region, even though he

wanted to compare them specifically to arm-

pit swabs.

Small smelly samples

Callewaert has previously been criticised

for overstating findings from limited data. In

another study of only nine people, he looked

at the effect of deodorants and antiperspi-

rants on armpit microbiomes and claimed that

the cosmetics “may actually make you smell

worse” (

Arch Dermatol Res

, 306:701). He later

admitted that the sample size was rather small but that he did

see “consistent outcomes” (

Washington Post

, 13/08/2014).

In the case of his T-shirt study, surely it would have been

better, given the unique microbiome in each person’s armpit, if

he had directly compared their T-shirts and armpit swabs. Fur-

thermore, he could provide standardised T-shirts for each par-

ticipant – one in cotton, one in polyester. Like that he could di-

rectly assess the match between armpit and textile; he could

even specifically amplify the armpit growth by cutting-out the

armpit regions of these T-shirts before incubating them.

But then, Dr Armpit does describe himself as a “pioneer”

and seems to be in a great hurry to be the first to cover new

ground. He even told the

Washington Post

that his ultimate ob-

jective was to solve the problem of body odour “by transplant-

ing microbes from non-malodourous relatives to those afflict-

ed”. Family armpit swaps could give a whole new sense to the

expression ‘keeping it in the family’!

Research Letter from:… Belgium

The Armpit Doc will Smell you Now

By our corresponding author,

Winderige Oksel

Photo: Fotolia/dandaman