How do you get the yellow underarm stains out of white tee shirts?
Hi Rachel: Fill a spray bottle with undiluted distilled white vinegar and keep it on hand in the laundry room to renove perspiration odor and stains on washable clothing. Spray the vinegar directly on the fabric on the inside of the underarm areas and allow it to work for at least ten minutes before tossing the garment into the washing machine. If the fabric feels stiff before washing, use a soft-bristled brush to break up the residue. The vinegar will help to cut through residual deodorant left on clothing and prevent underarm yellowing.
Here's a site that addresses this issue, also: https://clark.com/family-lifestyle/remove-yellow-armpit-sweat-stains/
You are very welcome. Hope it works for you!