Why does my gym kit still smell after washing?

Polyester and nylon are oleophilic — they attract and hold oil. Sweat itself is nearly odourless; the smell comes from bacteria digesting the sebum that transfers off skin into the fabric. Ordinary washing removes water-soluble soil, so it leaves the oil behind, and the smell reappears the moment body heat warms the garment.

What you'll need

• White vinegar
• Biological detergent
• A mesh laundry bag (optional)
• A washing line or airer

Step by step

1. Stop using fabric conditioner on activewear.It works by depositing a waxy coating on the fibre. On synthetics that coating traps the oil underneath it, blocks moisture wicking, and makes the smell permanent.
2. Get it out of the bag immediately.Damp kit in a sealed bag is an incubator. Hang it to dry as soon as you get home even if it will not be washed for days.
3. Soak in vinegar and water before washing.One cup of white vinegar in a basin of cold water, for thirty minutes to an hour. The acid breaks the bond between the oil and the fibre and kills the bacteria.
4. Wash it separately from towels and cotton.Cotton lint clings to synthetics and holds smell, and towels need a different treatment. A separate load also lets you use the right dose.
5. Use a full dose of detergent, not extra.Under-dosing is common with small loads and leaves oil behind. Overdosing leaves residue that itself holds smell. Read the dose for your water hardness.
6. Wash at forty degrees, not thirty.Thirty is too cool to shift body oils from synthetics. Forty is the balance point — hot enough for the oil, cool enough not to damage elastane.
7. Use an extra rinse.Detergent residue in tight synthetic knit is itself a food source. An additional rinse cycle makes a noticeable difference.
8. Air dry rather than tumble drying.Dryer heat degrades elastane and can bake in any residual smell. Line drying, ideally in sunlight, both dries and deodorises.
9. Run a maintenance wash on the machine.A machine that has only ever run cool washes has a biofilm in the drum and seal, and it will transfer smell to everything. Ninety degrees empty, monthly.
10. Retire kit that is beyond rescue.Once bacteria have colonised the fibre structure of a cheap polyester shirt, nothing reliably removes it. Two or three treatments and then accept it.

Tips

• A specialist sports detergent is genuinely different — it is formulated to lift oil from synthetics rather than dirt from cotton, and it is worth it if you train often.
• Turn kit inside out before washing. The oil is on the inside face, which is the side that needs the water.
• Never leave a wet wash sitting in the machine. Two hours is enough for synthetics to acquire a smell that then needs the whole treatment again.

Common mistakes

• Adding fabric conditioner to make it smell better — It coats the fibre and seals the oil in underneath, so the smell gets worse over time, and it destroys the moisture-wicking that the fabric was designed for.
• Washing at thirty with a half dose — Neither the temperature nor the detergent concentration is enough to remove body oil from synthetic fibre, so every wash leaves more behind than it removes.

If it doesn't work

Questions people ask