Does stronger odor in clothing after it is removed mean that more living bacteria remain in the fabric? A study comparing cotton, wool, and polyester found that the two did not follow the same ranking. Polyester smelled strong, yet its bacterial counts declined relatively quickly during storage. Wool smelled weaker, although some bacteria persisted for longer.
The 2007 study investigated underarm odor retained in clothing in relation to fiber type, knit structure, and bacterial counts during storage. It suggests that “reducing bacteria will reduce fabric odor in the same way” is not a sufficient explanation.
Comparing nine fabrics at the same wearers’ underarms
The test fabrics were 100% cotton, 100% wool, and 100% polyester. Each came in three knit structures, interlock, rib, and single jersey, making nine fabrics in total. The fabrics had no antibacterial or similar finish. They were washed beforehand and sewn into the underarm areas of cotton T-shirts.
The wearers were five men aged 18–55 with jobs that were not purely sedentary. They wore the same test shirt for about eight hours on each of two consecutive working days. There were five wear periods, arranged so that each person experienced all nine fabrics. Conditions likely to affect odor were also controlled: participants avoided antiperspirants and deodorants from before the trial and used unscented soap.
After wear, the fabrics were divided into small pieces and stored at 20°C and either 40% or 65% relative humidity. Thirteen trained assessors rated odor intensity after one, seven, and 28 days. Bacteria were extracted from separate pieces and cultured to count general aerobic bacteria, Corynebacterium, and a subgroup of corynebacteria associated with underarm odor.
These counts represented bacteria that formed colonies under the extraction and culture conditions used. Measuring odor ratings and bacterial counts separately is central to the study.
Polyester smelled strongest and wool weakest
At every storage time, odor intensity was highest for polyester, lowest for wool, and intermediate for cotton. The overall intensity varied between wearers, but the fabrics showed a common ranking trend.
Knit structure also offered a clue. Thin, lightweight polyester single jersey tended to smell weaker than thicker, heavier interlock or rib fabrics. The authors suggested that skin debris and secretions may pass more readily through thin fabric to the next clothing layer, leaving less behind. Because passage of these materials was not directly measured, this remains a hypothesis explaining the structural difference.
Fabrics stored for different lengths of time were not smelled side by side in the same evaluation session. The appropriate interpretation is that the ranking between fabrics was still evident after 28 days, not that odor intensity remained completely unchanged for a month.
Bacterial persistence ran counter to the odor ranking
One day after wear, bacterial counts did not clearly differ between the three fibers. Their subsequent rates of decline did differ: culturable counts fell relatively quickly on polyester. For cotton, there was no clear difference between days one and seven, but counts decreased by day 28.
The decline was smaller on wool. General aerobic bacteria and corynebacteria overall decreased by day 28, but the odor-associated corynebacterial subgroup showed no clear difference across the three time points. Bacteria persisted even on the less odorous wool.
Counts also varied by wearer and wear period. Furthermore, at 20°C, there was no significant effect of 40% versus 65% relative humidity on counts on any culture medium. This was a limited humidity comparison and does not support conclusions about other conditions, such as clothes left wet.
The researchers also checked whether bacteria might simply be harder to extract from some fibers. In an additional experiment, they applied bacteria to all three fabric types and extracted them. The method was judged effective for each material, so no fabric-specific correction was applied to the main bacterial counts.
Clothing odor depends on what remains in fabric, not just how many bacteria it holds
These results show why it is difficult to explain the odor perceived from fabric solely by the number of living bacteria present when it is sampled. Odor compounds produced earlier by bacteria may remain, and fibers’ ability to take up compounds and release them into the air may also matter.
The authors interpreted fiber chemistry and physical morphology as important to odor retention and release. However, the main measurements were sensory ratings and cultured bacterial counts, not chemical analyses establishing which individual odor compounds caused the differences. Treating wool’s weaker odor as direct evidence of natural antibacterial action would also be inconsistent with these findings.
The conditions matter: untreated test fabrics were attached at the underarms of five men. Real clothing adds factors such as blends, finishes, thickness, layering, and laundering. Rather than ranking every garment by fiber name alone, the study encourages consideration of both fiber and fabric structure.
Summary
Among the cotton, wool, and polyester test fabrics, polyester smelled strongest and wool weakest. Yet bacterial counts declined relatively quickly on polyester during storage, while some bacteria persisted longer on wool. Thin, lightweight polyester also tended to smell weaker than thicker polyester.
Understanding clothing odor requires asking not only how many bacteria are present, but also how a particular fabric retains and releases the sources of odor. Measuring these two aspects separately is a major contribution of this study.
The original paper acknowledges Designer Textiles Limited for supplying fabrics. No separate funding or conflict-of-interest declaration was found in the text.
Reference
McQueen RH, Laing RM, Brooks HJL, Niven BE. Odor Intensity in Apparel Fabrics and the Link with Bacterial Populations. Textile Research Journal. 2007;77(7):449–456. doi:10.1177/0040517507074816
