It is very important to start with a strong caution: While adding aspirin to laundry is a popular internet “hack,” its effectiveness is highly debated, and it carries the risk of damaging your washing machine and your clothes if used incorrectly.
Aspirin is acetylsalicylic acid. When dissolved, it creates a mild acidic solution. While this can theoretically help with some stains, it is not a detergent and lacks the cleaning agents (surfactants, enzymes) needed to actually remove dirt and body oils.
Here is a breakdown of what people claim aspirin does in laundry, the risks, and a much safer and more effective alternative.
The “Hack” (What People Claim)
The most common claim is that dissolving a few aspirin tablets in hot water and adding it to a wash load can help remove underarm yellow stains from white shirts. The theory is that the acid in the aspirin helps break down the combination of sweat, aluminum from deodorant, and body oils that cause those stubborn yellow patches.
The Reality and the Risks
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It May Not Work: The concentration of acid from a few aspirin tablets is very low once diluted in a whole washer drum of water. It is unlikely to be strong enough to effectively tackle set-in stains.
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Potential for Clogs: If you throw whole aspirin tablets into the drum or the detergent dispenser, they may not dissolve completely. They can get stuck in the pump filter or leave grainy, undissolved residue on your dark clothes.
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Fabric Damage (Over time): While a mild acid is generally safe for cotton, repeated or prolonged use of acidic solutions can potentially weaken fabric fibers or affect the color of dyes.
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Warranty Issues: Putting anything other than approved laundry products (detergent, bleach, softener) through your machine could, in theory, complicate a warranty claim if the machine develops a problem.
A Better, Safer Alternative for Yellow Stains
If your goal is to remove yellow underarm stains from white shirts, there is a scientifically proven method that is much more reliable: A Baking Soda and Laundry Detergent Paste.
Why this works: The yellow stain is a buildup of oils and minerals. Laundry detergent contains enzymes to break down oils, and baking soda is a mild abrasive and deodorizer that helps lift the stain from the fibers.
The Method:
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Make a Paste: In a small bowl, mix 2 tablespoons of liquid laundry detergent (like Persil or Tide) with 2 tablespoons of baking soda. Stir until it forms a spreadable paste.
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Apply: Lay the stained shirt on a flat surface. Using an old toothbrush or your fingers, work the paste thoroughly into the yellowed underarm area.
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Let it Sit: Allow the paste to sit on the stain for at least 30 minutes. For very old, set-in stains, let it sit for an hour or even overnight. The enzymes need time to break down the oils.
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Wash as Normal: Throw the shirt into the washing machine and wash it in the hottest water the fabric care label allows. Check the stain before drying—if it’s gone, air dry or machine dry as usual. Do not put it in the dryer if the stain remains, as the heat will set it permanently.
In summary: Please avoid putting aspirin in your washing machine. It’s a risky, unproven hack. Stick to using proper stain removers or the baking soda paste method for treating specific stains before washing.