I've got a bunch of plain white t-shirts that I really like, but after a few washes they always get these gross yellowish stains in the armpit area. I've tried using different deodorants and washing them more frequently, but it still happens. What's the actual cause and is there a way to stop it from happening in the first place?
I've dealt with this forever - turns out it's usually a combo of sweat, deodorant buildup, and sometimes the aluminum in antiperspirants reacting with your skin chemistry, not just one thing. The best prevention I've found is letting shirts air dry instead of using heat (dryer heat sets the stain), using less deodorant than you think you need, and honestly switching between a couple different brands so one doesn't build up. If you're already getting yellowing, soak the armpits in white vinegar or hydrogen peroxide before washing - that actually breaks down the stain rather than just moving it around. And yeah, washing in cold water helps too since heat makes it worse.
The trick that actually works is treating stains with an enzyme-based stain remover or a paste of baking soda and hydrogen peroxide before washing - hit them while they're still wet if possible. The reason this matters more than switching deodorants is that once those stains set in through heat drying, they're way harder to shift, so speed matters. Going forward, let your shirts air dry instead of using the dryer, since heat basically locks the staining in, and consider using antiperspirant at night instead of morning - less product buildup during the day means fewer yellowing compounds accumulating.
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