Baking soda is the internet's favourite laundry hack. Half a cup in the drum and supposedly your kit comes out fresh. It's cheap, it's already in the cupboard, and it feels like the kind of old trick that ought to work.
So does washing gym clothes with baking soda actually do anything? Partly — but not in the way most articles claim, and not on the odour that ruins activewear.
What baking soda actually does
Baking soda is sodium bicarbonate, a mild alkaline salt. In a wash it raises the pH of the water slightly, which can give a weak detergent a small nudge, and it softens hard water a little by sequestering some of the calcium and magnesium.
It also neutralises acidic odours, which is where its reputation comes from. The sour note in a gym bag or a pair of trainers left in the car reacts with the alkaline bicarb and is genuinely neutralised. That's why an open tub works in the fridge.
What it doesn't do
Here's the problem: the odour trapped in synthetic gym kit isn't primarily an acidic surface smell. It's a residue problem.
Polyester and nylon are oleophilic — they attract and hold body oils. Sweat itself is nearly odourless; the smell comes from skin bacteria feeding on its proteins and lipids. Those oils bond into the fibre structure, and every wash that fails to remove them leaves a little more behind — until you get kit that smells clean out of the machine and then reeks the moment your body heat hits it.
Baking soda has no meaningful effect on that. It isn't a surfactant, so it doesn't lift oil from fabric, and it contains no enzymes, so it can't break down sweat proteins. It may neutralise a surface smell for a wash or two, but the underlying residue stays put.
There's a practical downside too. Bicarb doesn't dissolve well in a cold wash, so a large dose can leave gritty white residue on dark technical fabric. And combining it with vinegar — advice you'll see everywhere — is chemically pointless: an alkali and an acid neutralise each other into salty water and fizz. More on that in our guide to washing gym clothes with vinegar.
Where it's genuinely useful
Baking soda earns its place outside the machine rather than inside it. As a dry deodoriser it's good: sprinkle it into trainers overnight, vacuum it out in the morning, and it absorbs moisture and takes the sharpest edge off the smell. Same goes for a gym bag between uses. It's also a fair pre-soak booster for genuinely filthy kit — a couple of tablespoons in warm water for an hour before a normal wash.
What it isn't is a detergent substitute. If your kit already smells after washing, adding bicarb to the same wash won't change the outcome, because the thing that failed was the detergent.
What actually shifts embedded odour
Removing sweat residue from synthetics takes chemistry aimed at the problem: enzymes to break down the proteins and oils lodged in the fibres, and something that deals with odour molecules rather than covering them.
That's what Titan Wash is built for. It uses a high enzyme complex that targets sweat proteins directly, Zinc Ricineolate to bind odour molecules so they rinse away rather than lingering, and oxygenating agents to lift residue out of the fabric. There are no optical brighteners, no chlorine bleach and no phosphates — nothing that degrades elastane or strips a DWR coating. It's active from 20°C and works best at 30°C, which is where technical fabric wants to be washed anyway.
Use 30g straight into the drum, not the drawer, turn your kit inside out, and skip the fabric softener — it leaves a waxy film that traps the exact residue you're trying to remove. For the rest of the wash, see our guide to the best washing machine setting for gym clothes, or why gym clothes stink after washing for the residue problem in full.
FAQs
How much baking soda should I put in a wash?
One to two tablespoons in the drum is plenty. The half-cup doses recommended online leave white residue on dark fabric and don't clean any better.
Can I use baking soda and vinegar together on gym clothes?
No. An alkali and an acid neutralise each other, leaving salty water and fizz. Use one or the other — and neither removes embedded body oil.
Will baking soda damage activewear?
Not chemically, at sensible doses. The risk is physical: undissolved granules are mildly abrasive. Dissolve it in water first if you're going to use it.
Does baking soda work on trainers?
Yes, better than it does in the wash. Dry bicarb left in a shoe overnight absorbs moisture and neutralises acidic odour. It's maintenance, not a deep clean.
The short version
Baking soda is a decent deodoriser and a poor detergent. It'll freshen a gym bag or a pair of trainers, but it won't strip sweat residue out of polyester — it has no mechanism for doing so.
If your kit still smells after washing, the fix is a detergent formulated for the fabric. Titan Wash is £14.99 for a 750g pouch — 25 washes, 60p a wash, dropping to 49p on the 3-pack. There's a trial sample at £2.95 if you'd rather test it on your worst kit first.