White vinegar helps to eliminate yellowing from sheets. Over time, body oils and sweat accumulate in white sheets, making them yellow, even when washed in hot water.
Creating a solution of white vinegar and water makes a helpful pretreatment for white sheets that have yellowed a bit. Spraying the yellowed parts with the solution starts to eliminate the stains before putting the sheets into the washing machine.
The sheets should be washed in a hot cycle, but the machine should be paused when the tub is full, either by the user opening the lid or pushing the dial back in. The sheets should soak until the water starts to cool. Check the sheets before putting them in the dryer to see if the yellowing is gone.