Why do clothes that are dried in the shade smell so bad? The reason is...

When the rainy season comes, friends in the south will face an extremely painful thing: they can't see the sun for several days in a row, and the washed clothes can only be dried in the shade.

Clothes that are dried in the shade are not only damp and uncomfortable to wear, but more frustratingly, they always have a moldy smell.

Many people are troubled by this. Yesterday, “Why do clothes dried in the shade smell so bad” became a hot topic on Weibo.

Image source: Sina Weibo

Many netizens said that the stench was indescribable, and it hit them in the face without getting close to smell it. It was like something rotten, like rotten pickled cabbage, and a bit like stinky feet...

Why do clothes that are dried in the shade smell so bad? How can we get rid of this bad smell? Let's talk about it in detail today.

01

Why do clothes that are dried in the shade tend to smell bad?

We know that the biggest feature of the rainy season is high humidity , which provides a basis for the survival and rapid reproduction of microorganisms such as fungi and bacteria.

At this time, as long as there is a little "nutrient", such as sebum and dandruff remaining on the clothes, fungi, bacteria and other microorganisms can multiply in large numbers, thus producing odor.

Many people may wonder: The clothes have been washed, so why are there still sebum and dandruff? Are they not washed clean?

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Yes, every time we wash clothes, even if we have soaked and cleaned them carefully, even if we wash them for a long time, and use detergent with good cleaning ability, it is still impossible to remove 100% of the residues on the clothes, including sebum and microorganisms .

Studies have found that various microorganisms adhere, grow and secrete extracellular matrix on the surface and gaps of textiles to form biofilms. Although regular cleaning can maintain hygiene, it cannot remove microorganisms that have already formed biofilms.

The degree of attachment of E. coli to textile surfaces with two different fiber diameters and layer depths. Top: PET-SB, bottom: PP-MB. Image source: Reference [2]

Moreover, even the smoothest textiles, when magnified hundreds of times, are made up of a certain number of fibers according to a certain weaving process. The rougher and more twisted the fibers are, the easier it is to harbor dirt, the harder it is to wash clean, and the more likely it is to have microorganisms and sebum residue.

Scanning electron microscope micrographs of different fibers, in order: coarse wool, fine wool, silk, linen, cotton, polyester. Image source: Reference [5]

From the magnified surface structure of different clothing materials, we can clearly see that natural fibers are more difficult to wash clean, such as wool, silk and cotton.

In addition, in general, natural fibers have higher hygroscopicity than chemical fibers. At a certain humidity, natural fibers are more likely to provide bacteria with a suitable humid environment.

But even if it is natural fiber, on a dry, sunny day, if the clothes are washed and dried in time, even if there are some microorganisms and sebum left, it will not have any effect.

But in the warm and humid rainy season, the situation becomes different. The humid environment + the residual nutrients "sebum" + the suitable temperature are simply a paradise for various bacteria, fungi and other microorganisms. They have no worries about food and water, reproduce in large numbers, and also produce an indescribable "stink".

In particular, a type of bacteria called "Morabilis Oslo" is different from other common bacteria in that it is an aerobic bacteria and has good resistance to dryness and UV rays.

During the rainy season, even if you are lucky enough to see the sun from time to time, bacteria such as Escherichia coli and Staphylococcus aureus can be killed, but Moraxella osloensis can still survive.

Even after the clothes have finally dried in the shade, the moisture content of the fabric has decreased and most bacteria and mold have stopped growing, but Oslo Moraxella can still actively jump around.

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What’s even more frustrating is that this kind of bacteria can also metabolize many unpleasant substances, such as intermediate alcohols, aldehydes, acids, etc., especially some unsaturated fatty acids, which are the main source of odor.

This is also why clothes dried in the shade have an indescribable odor that takes a long time to dissipate.

02

Two ways to effectively remove odor from clothes

How can we eliminate this odor? There are two reliable and feasible methods .

1. Drying

High-temperature drying can effectively kill bacteria and fungi to a certain extent. At the same time, drying can greatly shorten the drying time of clothes during the rainy season and can effectively remove odors caused by microorganisms.

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2. Use long-lasting antibacterial agents when washing clothes

When it comes to washing clothes, sterilization is important, but after the clothes are washed, it is more important to inhibit the reproduction of bacteria for a long time.

Conventional detergents only have the ability to remove stains and often require additional disinfectants for disinfection and sterilization, but they cannot achieve long-term antibacterial effects.

To deal with the odor of clothes drying in the shade, you can also find special long-lasting antibacterial detergents, so that even if the clothes are dried in the shade, it is not easy to produce odor.

References:

[1] Niwano Yuu, Takeuchi Hirohei, Yue Xiao. Analysis of the causes of clothing "dry odor" and development of deodorizing fabric care products [J]. China Detergent Industry, 2013, No.144(02):60-64. DOI:10.16054/j.cnki.cci.2013.02.009.

[2] Hemmatian T, Kim J. Quantification Methods for Textile-Adhered Bacteria: Extraction, Colorimetric, and Microscopic Analysis. Polymers (Basel). 2019 Oct 12;11(10):1666. doi: 10.3390/polym11101666. PMID: 31614838; PMCID: PMC6835282.
[3] Van Herreweghen F, Amberg C, Marques R, Callewaert C. Biological and Chemical Processes that Lead to Textile Malodour Development. Microorganisms. 2020 Oct 31;8(11):1709. doi: 10.3390/microorganisms8111709. PMID: 33142874; PMCID: PMC7692034.
[4] JDenawaka C, AFowlis I, RDean J. Source, impact and removal of malodour from soiled clothing[J]. sciencedirec, : https://doi.org/10.1016/j.chroma.2016.02.037.
[5] Dunn AG R. Review articles A review of clothing microbiology: the history of clothing and the role of microbes in textiles[J]. , 13 January 2021: https://doi.org/10.1098/rsbl.2020.0700.

Author: Sun Yafei, Distinguished Research Assistant at the Institute of the History of Natural Sciences, Chinese Academy of Sciences, PhD in Chemistry, Tsinghua University

Audit｜Song Lidan Consulting Engineer, Industrial Research Department, China Textile Construction Planning Institute

Planning editor: Lin Yiyi

Editor in charge: Lin Lin