How do you get the yellow stains in the arm pits out?

White vinegar mixed with laundry detergent. Put it on the stain and scrub with an old toothbrush or fingernail brush, then wash as you normally would.

You might consider changing deodorant. When I changed to SURE it stopped the pit stains.

The dryer may have heat set the stains into the fabric, but you can try OxyClean. I have soaked a couple of items in a strong solution of OxyClean and gotten out pit stains and collar stains. Heat set stains are more difficult, but give it a shot.

I have found the easiest way to avoid this staining is to launder my whites and pastels every time I wear them. Since I started doing that, I have not had a problem with the staining.

Even if they are hand laundered in Woolite, the stains don't happen. Good luck!

Yellow underarm shirt stains are likely caused by a combination of deodorant and perspiration. Many deodorants and antiperspirants contain aluminum salts. When these salts are combined with laundry detergent, especially in cooler water settings, they are not easily dissolved, and they remain on the fabric.

To remove the stains, try soaking the shirts in warm water with an enzyme pre-soak product or rubbing the soiled area with white vinegar. Wash in the hottest water safe for the fabric. If the stain remains, dampen and sprinkle stain with meat tenderizer. Let stand for about an hour, and launder again.

To avoid new stains from forming, always wash the shirts in the hottest water safe for the fabric. Also, allow antiperspirant to dry completely before dressing.:)

Try making a paste out of baking soda and water and rub that on the stain. Then wash as usual. It works on my hard to clean polyester knits.

if the shirt is white use hot water and chlorine bleach

I correct my aim.