What's actually causing those yellow marks
Here's the bit most people get wrong: it's usually not sweat on its own turning your white shirts yellow — it's the aluminium in antiperspirant reacting with the proteins in your sweat. That chemical reaction is what leaves that stiff, yellowed patch under the arms, and it builds up over time with every wash if it's not treated properly, which is why it seems to get worse the older a shirt gets.
Fresh or recent stains
- Mix a paste of equal parts baking soda, hydrogen peroxide and a colourless (not blue or dyed) dish soap.
- Work it into the stain with an old toothbrush, really getting it into the fabric.
- Leave it 30 minutes to an hour. This isn't a five-minute job — give it time to actually break down the residue.
- Wash on the warmest temperature the fabric allows. Warmer water helps here, unlike a lot of other stains on this list.
- Check before drying — same rule as always, don't let heat set anything that's still there.
Built-up, older yellowing
For shirts that have gone yellow over months (or years, let's be honest) of wear, soak the underarm area in a mix of one part white vinegar to four parts warm water for a few hours, or even overnight for a really stubborn build-up. Vinegar's mild acidity helps break down that mineral and protein residue that's baked in over time. Follow up with the peroxide-baking soda paste from above, then wash as normal.
What not to do
- Never mix hydrogen peroxide with vinegar directly — do one, rinse thoroughly, then the other if needed. Combined they can create a mild peracetic acid that's not something you want on your skin or in an unventilated laundry.
- Don't use hydrogen peroxide on coloured or dark clothing — it will lighten it, and there's no undoing that.
- Don't skip straight to bleach hoping it'll be faster — it can actually make the yellowing worse on some fabrics by reacting with the aluminium residue.
- Don't iron over the stain before it's fully treated — heat sets it just like everything else on this list.
Fabric-specific notes
This method is really built for white cotton or poly-cotton work shirts. Silk and wool are a hard no for hydrogen peroxide — it'll damage the protein fibres in wool and can bleach silk unevenly. For delicates with sweat staining, a gentle enzyme-based pre-soak is a safer bet, and honestly, for a good silk shirt it's worth getting it professionally cleaned rather than risking a DIY mix.
Prevention (because this one's easy to avoid)
Letting antiperspirant fully dry before dressing, and washing white shirts after every wear rather than "getting a couple more wears out of it" both make a real difference. Once that yellow staining has properly set in over multiple wash cycles, it gets a lot harder to fully reverse — so if you've got shirts starting to show it, treat them now rather than later.
When it's beyond a DIY fix
Deeply set-in yellowing on shirts you've worn for years often needs more than a kitchen-cupboard fix. If you've got a stack of work shirts in that state, it's genuinely easier to hand them over — our wash & fold service can pre-treat stubborn stains properly, and if it's a regular problem, a weekly or fortnightly pickup means it never gets the chance to build up in the first place.
Common questions
Will switching deodorants fix the yellow stains?
It can help going forward — aluminium-free deodorants won't cause the same chemical reaction with sweat. It won't do anything for shirts already stained though, those still need treating.
Can I use hydrogen peroxide on coloured shirts?
No — stick to white or very light, colourfast fabric only. On dark or coloured clothing it will bleach and leave patchy, uneven spots that are worse than the original stain.
Why do the stains keep coming back after washing?
Usually because the wash cycle alone isn't enough to break down the aluminium-protein residue — it needs the pre-treatment step first. A hot wash on its own often just sets whatever's left behind, which is why the stains seem to reappear or get more stubborn each time.
Got a stain that's beaten you? Bag it up and let us deal with it — our wash, dry & fold service handles the tricky loads too, and we'll flag anything that needs special care before it goes anywhere near a dryer.
Book a Laundry PickupSources: Tom's of Maine, Degree, Whirlpool, Red Kap workwear-care guides and general cleaning-science consensus on antiperspirant/protein staining. Fact-checked 29 July 2026. General guidance only — always check your garment's care label first.