While we use these words like they mean the same thing. They really aren't. And for technical fabrics, the gap between them matters a lot.

Standard laundry detergent is a synthetic product built from petroleum-based compounds. The ingredient list typically includes surfactants like sodium lauryl sulphate (SLS) or sodium dodecyl sulphate (SDS), plus enzymes, optical brighteners, bleaching agents, and artificial fragrance. These are designed to be powerful — and for heavy cotton or denim, they do the job.

But for anyone with sensitive skin or eczema, that ingredient list is a real problem. It was found in a study done in 2023 that SDS are known irritants that they can lead to higher levels of inflammation which can in turn trigger eczema flares. When using a synthetic detergent, SDS is usually left behind in fabric (which they are, because synthetic detergent doesn't fully rinse out of tightly woven fibres), they sit against your skin for hours during a workout. That's a significant amount of contact time with ingredients your skin is already reacting to.

And beyond the skin concern, there's the fabric problem. Synthetic fibres like polyester naturally attract body oils and sebum at a molecular level, which is exactly where odour-causing bacteria feed and multiply. Detergent residue builds up in those same fibres and coats over those trapped oils rather than lifting them away, meaning each wash becomes less effective than the last. That's why gym wear can smell clean straight out of the machine and reactivate the moment the fabric warms up against your skin.

Let's get into it, because once you see this you can't unsee it.

Technical fabrics repel water, which is what makes them so good at moisture-wicking during a workout. But that same property means synthetic detergent doesn't fully rinse out either. It accumulates in the weave, and bacteria get sealed in behind it. Each wash makes the buildup worse. That's the cycle: smells fine, turns funky five minutes into your workout. 

That stiff, almost cardboard-like texture after washing, especially around the waistband, is a sign of fibre damage. The bleaching agents and harsh surfactants in conventional detergent break down fibres over time. And not only that is cumulative, it also is unfortunately not reversible.

Using extra detergent doesn't mean cleaner clothes and your machine can only rinse out so much per cycle. Whatever's left stays in the fabric, adding to the buildup, speeding up the damage. With technical wear, less is genuinely more. And when clothes feel stiff and crispy from the build up, it is understandable that reaching out for a softener is a solution. But fabric softener deposits a coating over technical fibres that blocks moisture-wicking and breathability, the exact things you're paying for. For gym wear, better to skip it altogether.

Not all laundry soaps are created equal. For technical gym wear, there is a need to focus on what works well and to prolong the longevity of your expensive Lululemon and Alo. If your skin is sensitive or eczema-prone, the ingredients in your laundry soap matter just as much as what's in your skincare. Here's a quick overview of what you want — and what to avoid:

When it comes to the cleaning base, saponified coconut and olive oils are what you want to see on the ingredient list. They clean effectively without leaving synthetic residue behind in the fabric, and they don't degrade the technical properties of the fibre over time. So even after washing multiple times, there is no buildup nor damage to the clothing.

For odour, sodium bicarbonate is the ingredient that actually does the work. Baking soda is alkaline, which means it actively inhibits bacterial growth and neutralises the compounds that cause smell at the source, rather than layering fragrance over the top of them. For gym wear specifically, this is what makes the real difference. If it's not on the label, the soap is most likely masking odour rather than eliminating it.

On the avoid list: SLS, SDS, bleaching agents, enzymes, and optical brighteners, both for skin health and fabric longevity. SLS and SDS are known irritants that compromise the skin barrier, particularly for eczema-prone skin. Optical brighteners and bleaching agents are equally common in mainstream laundry products and carry the same concerns. They also gradually strip colour and break down performance fibres in activewear. 

Finally, a laundry soap that sits in fabric fibres and then sits against your skin for an hour-long workout needs to be genuinely non-irritating, not just marketed as 'gentle.' Look for formulas that are dermatologically tested. And if there is a fragrance, it should be light and naturally derived rather than synthetic and masking.

Kerzon's Gym Tonique meets all of these, saponified plant oils, baking soda as the odour neutraliser, no bleaching agents, enzymes, or optical brighteners, and a citrus and juniper scent that's energising without being overpowering. 

The right soap does most of the work, but a few simple habits alongside it go a long way.

For elasticity

• Wash inside out as it reduces friction on the outer surface during the cycle
• Air dry only, heat is the single biggest enemy of elastane; even a low tumble dry setting accelerates fibre breakdown over time
• Use a laundry soap (made from natural saponification) rather than conventional detergent as it keeps stretch intact wash after wash

For colour

• Cold water, always as heat causes dye molecules to release, which is what gradually dulls colour
• A soap with no bleaching agents means colours stay saturated over time rather than washing out

For odour

• Don't let sweaty gym wear sit bunched up, bacteria multiply quickly in warm, damp conditions; hang or lay flat before washing
• A baking soda-based formula neutralises odour at the source rather than masking it
• Pour the laundry soap into the detergent drawer, not the drum, effective from 30°C upward, no hot wash needed
• Skip the fabric softener, a good soap formula conditions fibres naturally