Why do synthetic garments – especially tracksuits, lined jackets and trainers – smell of sweat even after washing? The founder of the laundry brand Pure Effect, Linda Rosendahl Nordin, gives us more insights about fibers and the role bacteria can play in both the creation and elimination of bad odor.
Synthetic materials like polyester and polyamide are comfortable, durable, and dry quickly. But the very properties that make them practical for everyday wear also create the perfect conditions for sweat odor to settle in and linger.
Let's go through what actually happens in the material – and how you can manage it in a more sustainable way.
1. Synthetic fibers are hydrophobic – and bind fat-based odor molecules
Polyester and polyamide repel water but readily bind lipids (fats). The most troublesome sweat odors come from fat-soluble molecules that are formed when skin bacteria break down the fatty acids in sweat, such as isovaleric acid, 4-methyl-3-hexenoic acid, and certain thioalcohols. Because the fiber is hydrophobic, these substances stick more easily to synthetics than to natural materials like cotton.
2. Microscopic pits in polyester encapsulate odors
To the eye, synthetics look smooth, but under a microscope, you can see small pits and irregularities where skin oil, deodorant residue and bacterial residues can penetrate and become encapsulated in the fiber. From there, it is difficult for water and detergent to reach them. This is why freshly washed synthetic garments sometimes “come to life” and start to smell again when they are warmed up by the body.
3. Fast drying time means the smell stays put
The quick drying removes the moisture, but the fat-based odors remain in the material. Cotton buffers moisture more and can release odor molecules more easily when washed and aired.
4. Why traditional washing doesn't help
Traditional detergents are designed to dissolve dirt, pigments and water-soluble residues – not to break down fat-bound, odorous molecules. Chemical cleaning also does not solve the problem, as the solvents do not reach the biological residues inside the fiber.
What you can do
Treat the place where the odor is
In many garments, especially jackets, it is the lining (often polyester or acetate - semi-synthetic material) that carries the smell - not the outer fabric. Spray liberally on the inside, in the armpits, back panel and shoulders. The Bacillus bacteria in the Pure Effect spray produce enzymes that break down the odor molecules instead of masking them. It works especially well on synthetics, as the problem is precisely biological residues in the fiber. Let the garment air dry. The same procedure applies to shoes where Pure Effect can work wonders .
Repeat for vintage or older garments
Garments with years of built-in odor often need 2–3 treatments. This is especially true for tracksuits and vintage jackets.
Use steam to open the fibers
Steam can soften the fiber slightly and release odorous substances so that the bacteria in the spray can reach them better.
Avoid deodorant overdose
Many modern deodorants contain aluminum and silicone components that, together with polyester, can form a tough film inside the fiber.
Wash less. Spot treat more
Frequent washing of synthetics is both ineffective against odor and wears out the material. Instead, treat locally and air between uses.
Summary
Sweat odors stick to synthetics because the fiber structure and chemistry make it easy for fat-based odor molecules to get in – and difficult for water and detergent to get them out. By understanding where the odor is, and using methods that actually break down the odor molecules biologically, it is possible to get synthetic garments fresh again without washing them. Try Pure Effects spray today !
Text and image: Pure Effect
