Treating Sweat Stains on Shirts
Underarm stains can involve perspiration, body oils, and deodorant or antiperspirant residue. Their appearance alone does not establish a safe treatment for every shirt. Follow the item's care limits, choose a compatible method, and inspect the fabric after washing. A fresh scent is not proof that visible buildup has cleared or that heated drying is now appropriate.
Buildup changes the fabric
Maytag explains that perspiration, body oils, and deodorant ingredients can contribute to underarm discoloration over time. The guide recommends addressing buildup promptly and checking the care label before treatment, particularly where professional cleaning is required. A visible yellow mark is not a reason to ignore those restrictions.

Air drying supports inspection
The source describes soaking and stain treatment, followed by washing and air drying while evaluating progress. It warns that chlorine bleach may darken sweat stains rather than solve them. Repeat a suitable process if needed before returning the garment to a permitted heated drying cycle, instead of setting an incompletely removed stain with heat.
GarmentCare Guide 