If you have a white T-shirt, you probably know this: sweat stains are almost unavoidable. You wear it just one time, and it's already going into the laundry basket. Then later you pull it out with a slight yellow ring under the arms that just won’t come out. Turns out, there’s a laundry hack that’s been quietly making the rounds online for years: dissolve aspirin tablets in water and soak your clothes in it. McGill University's Office for Science and Society says the trick is so popular that people have debated whether it really works or if it is just laundry room folklore.
Here is what is really going on, why those yellow marks show up, and whether that bottle in your medicine cabinet deserves a spot next to your detergent.
Why your white shirts turn yellow in the first place
Sweat itself is fairly colorless. The yellow color shows up because of a reaction, not because sweat is dirty. According to the Dry Cleaning and Laundry Institute International, perspiration contains salts, amino acids, and other compounds that oxidize when exposed to heat, such as an iron or dryer, and that oxidation is what turns fabric yellow over time. Most antiperspirants also contain aluminum-based compounds, and when those combine with sweat and body oils, they leave a residue that sticks to fabric fibers, which is why stains are usually found right under the arms.
So it’s not really a regular old “sweat stain.” It’s a slow chemical process, which is also the reason why normal detergent alone is often not enough once it has set in.
