We’ve all looked at a favorite white shirt and noticed the underarms have yellowed. Deodorant isn’t the greatest factor. Sweat isn’t the only culprit. Aluminum-based antiperspirants cause cells in your sweat ducts to swell and block sweat from escaping. When the chemical compounds binds with sweat, you’re likely to get stains. Some ways to avoid ruining your new summer whites are: stick with deodorant alone; find an antiperspirant without an aluminum-based compound; avoid gel and roll-ons; apply your antiperspirant in a very thin layer and wait for it to dry completely before dressing or put it on at night before bed.
If you want to save the garment you can try pre-soaking delicate fabrics in an ammonia/water solution. Ammonia is alkaline and will help neutralize the acidic antiperspirant. A set-in stain on a durable fabric needs a pre-soak in a baking soda/ water/white vinegar solution. Dry clean only fabrics are best dealt with by your neighborhood dry cleaner.