White shirts are a commitment. You buy one, you wear it twice, and then there it is — the yellow ring around the collar and the faint yellow shadow under the arms.

I ruined three white dress shirts before I figured out what was happening. It is not sweat that stains. It is the aluminum in your antiperspirant reacting with your sweat.

The Right Fix

Mix equal parts hydrogen peroxide (3 percent), baking soda, and water into a paste. Scrub into the stain with an old toothbrush. Let it sit for 30 minutes. Wash in cold water.

For older stains, soak the shirt in undiluted white vinegar for 30 minutes first. Vinegar dissolves the aluminum salts.

Crush two uncoated aspirin tablets, mix with warm water, and apply. Aspirin is acetylsalicylic acid — chemically similar to some stain removers. My travel trick.

Prevention

Switch to an aluminum-free deodorant. No aluminum means no reaction, means no yellow stains. Or apply antiperspirant at night before bed instead of right before you dress.

I switched to aluminum-free deodorant six months ago. Took about two weeks for my body to adjust. Now my white shirts stay white. No more yellow armpit line.