Why does polyester start to smell and why is old sweat odor so hard to remove?

The garment is freshly washed and smells clean, but after a short while on the body, that old sweat odor returns. This happens often with workout clothes, but by no means only there. It could be polyester tops that quickly start to smell under the arms, blouses that feel stale sooner than they should, or jackets that are clean but where the polyester lining starts to smell as soon as it warms up against the body.

The phenomenon is sometimes called permastink. The explanation is more complex than old sweat simply remaining in the garment. The material interacts with skin oils, sweat and other organic residues, microorganisms, moisture, and temperature. Furthermore, we who wear the garment play a role.

A further explanation can be found if we view the textile as a small microbial ecosystem, where all these factors influence one another.

Why does polyester start to smell of sweat?

Fresh sweat smells relatively little. The typical sweat odor arises primarily when microorganisms metabolize substances from sweat, skin oils, and other secretions, forming substances that we perceive as odor.

When a garment lies against the skin, sweat, skin oils, skin cells, bacteria, and other microorganisms are transferred to the textile. There, they encounter a material with its own unique properties. Add moisture, heat, and time, and we have an environment where odor can develop.

Polyester is particularly interesting. The material is hydrophobic, which simply put means that it does not attract and bind water the same way as cotton, for example. However, polyester more easily absorbs oils and other fat-soluble substances. In a study of cotton and polyester, researchers observed that skin oils were distributed along the polyester fibers and between the fibers. They also saw that more bacteria attached to polyester than to cotton.

It is therefore too simple to say that the sweat has "gotten stuck in the polyester." What happens is an interplay between material, organic residues, microorganisms, moisture, temperature, and the individual.

The textile as a microbial ecosystem

Different materials create different conditions for microorganisms. In a study where 26 people worked out in, among other things, polyester and cotton, the polyester garments smelled both stronger and less pleasant afterward. The researchers also observed differences in which microorganisms established themselves on the materials.

At the same time, the material is only one part of the system. We humans have different microbiomes on our skin and produce different amounts and compositions of sweat, skin oils, and other secretions. In a study of used cotton and polyester shirts, researchers found that the individual wearing the garment influenced the textile's microbiome more than both the material and the wash.

Even genetic variations can affect which substances the body secretes and thereby the conditions for body odor. This does not mean that our genes determine how a garment will smell, but they are an additional factor in a system that is more individual than one might first think.

The same polyester top can therefore develop odor in different ways depending on the person.

Why polyester can easily develop sweat odor

Professor Vincent Nierstrasz, Professor of Textile Materials Technology at the University of Borås, explains the properties of polyester and the microbial interactions that lie behind it:

"Polyester has different surface properties from materials such as cotton and more readily takes up fats and other fat-soluble substances from the body. At the same time, a textile can act as a small microbial ecosystem, where the material interacts with organic residues, microorganisms, moisture, temperature and the person wearing the garment. This helps explain why polyester can easily develop odour and why it can persist after repeated wear and washing. The compounds responsible for these odours are often produced by bacteria and can themselves be hydrophobic, which makes them adhere particularly well to polyester, and difficult to remove."

Why does polyester still smell after washing?

This is where we arrive at what is sometimes called permastink. The garment comes out of the wash and smells clean, but when you put it on and the material becomes warm and damp, the old smell quickly returns.

One explanation is that the wash has not removed everything that remains in the textile. Organic residues, microorganisms, and certain odorants may remain even after washing. Research on repeated soil-and-wash cycles also shows that certain odorants can be harder to remove from polyester than from cotton, and that odorants can accumulate over several cycles.

When the garment then returns to the body, the environment changes again. Heat and moisture are added along with new organic residues and microorganisms from the skin. This can contribute to a garment that smells clean when dry quickly starting to smell of old sweat again.

The history of the garment also plays a role. A garment that has recently started to smell does not have the same starting point as a polyester top, a jacket lining, or a workout shirt that has been used and washed many times. Repeated cycles of use, drying, and washing can make the odor problem significantly more complex.

Textile odor is therefore not a single substance to be neutralized. It is the result of a biological and material-technical system that has evolved over time.

How to remove sweat odor from polyester?

Here we start at the same end as always at Pure Effect:

Odor is not the problem. The problem is organic residues that odor-producing bacteria feed on.

Pure Effect Textile Spray contains selected spores of Bacillus subtilis and is based on biotechnology. When the conditions are right, biological processes contribute to breaking down organic residues that odor-producing bacteria would otherwise feed on.

Textile Spray therefore works on the conditions behind the odor instead of just masking it with perfume. It can be for workout clothes after a run, but just as well the polyester top you want to use again, the dress that doesn't need to be washed, or the jacket where the lining has started to smell. Spray. Wait. Use again.

What to do about really deep-seated sweat odor?

With old and deep-seated odors, more time may be needed. Feel free to start with a clean and dry garment and treat primarily the area where the odor is, for example under the arms, on the back, around the collar, or in a jacket lining. Then let the Textile Spray have time to work and the garment dry properly.

With really stubborn odors, the treatment may need to be repeated. More product at once is not necessarily better. Time and repetition can be more important. An older polyester garment with many years of use and washing behind it may simply have significantly more difficult conditions than a garment where the odor problem has just begun.

Sometimes we cannot remove all the odor. Textile Spray cannot be expected to provide the same results on all materials and garments because the starting point can be so different. This is also an important part of understanding permastink. When an odor problem has built up over a long period, it can be significantly harder to solve than treating odor early.

Prevent sweat odor before it sets in

The best thing is therefore not to wait until your favorite garment has developed really severe permastink. Let damp garments dry properly, deal with odor when it arises, and distinguish between odor and dirt.

A garment that smells does not automatically need a full wash. Sometimes it needs to be aired out, sometimes the odor needs to be treated, and sometimes it, of course, needs to be washed. Making that assessment between wear and wash is especially valuable for jackets, dresses, and other delicate or difficult-to-wash garments that we neither can nor want to wash after every use.

By dealing with odor early, we can help the garment stay fresh between washes and keep it in play longer. Use more, and wash less.

 

FAQ - Common questions about sweat odor in polyester

Why does polyester smell more of sweat than cotton?

Polyester has different surface properties than cotton. The material more easily absorbs oils and other fat-soluble substances and also influences how microorganisms attach and behave in the textile. Together, this can create conditions for odor to develop and become harder to remove.

Why do clothes smell of sweat immediately after washing?

The wash may not have removed all organic residues, microorganisms, and odorants. When the garment then becomes warm and damp against the body, the environment in the textile changes again and the odor can quickly become noticeable.

Does permastink only apply to workout clothes?

No. Workout clothes are a clear example because they are exposed to a lot of sweat, heat, and moisture, but the same problem can arise in, for example, polyester tops, blouses, dresses, and polyester linings in jackets.

Why does the same polyester garment smell different on different people?

We have different skin microbiomes and different compositions of sweat, skin oils, and other secretions. Research on used T-shirts shows that the individual can have a great impact on the textile's microbiome. Genetic factors can also affect the conditions for body odor.

Can you get rid of old sweat odor from polyester?

Often it is possible to reduce or remove the odor, but the result depends on the material and the history of the garment. With old and deep-seated odor, the treatment may need to be repeated, and sometimes not all the odor can be removed.

 

 

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