1. Thicker applications of any deodorant or antiperspirant aren’t necessarily more effective, ad they instead the chances of you getting those stain causing chemicals on your clothes. Applying a very thin, even layer of antiperspirant to your armpits will help prevent the acids and aluminum salts from getting on your clothes.
2. Before donning your daily attire, make sure to let the deodorant or antiperspirant dry thoroughly. This may require you to walk around the house without a shirt on for a while, but if your significant other complains, just tell them you’re saving them from an agonizing day in the laundry room.
3. Try using just plain old cold water to rinse the armpits of your shirts when you get home. Apparently cold water is just enough to neutralize the acids eating away at your shirts, and simply soaking the armpits before putting your shirts in the wash should help keep your shirts free of sweat stains.
4. These stains are particularly bad when you use the new extra strong medical antiperspirant out there. I have found that if you do the above steps and also put a little bit of concentrated laundry detergent on an old toothbrush, wet and scrubs the stained areas. Let this set for about 20-30 minutes before washing. Also, if you have a lot of white shirts like this, feel free to pretreat the area as described and add a little bit of diluted bleach to the areas.
5. IF the shirts are white, I recommend doing this and allowing the shirts to set in warm water with laundry detergent and 2 caps of bleach..