There are many reasons why white fabrics yellow: Storage in dark places, body oils, or simply the ravages of time can turn bright whites into grungy garments. To whiten them again, try this simple bleach-and-hot-water method.
Check care label to make sure the fabric is bleach-safe.
Soak overnight in an enzyme presoak, which will immediately go to work breaking down organic materials to augment the cleaning process later.
Set washer to as hot a temperature as tolerable by the fabric (see care instructions on clothing).
Use twice as much (bleach-safe) detergent as usual.
Add chlorine bleach 5 minutes after the wash cycle has begun.
Hang in bright sunlight to dry.
Before use of chlorine bleach, dilute as directed on the product's label.
Chlorine bleach can end up yellowing fabrics such as wool, spandex, nylon, silk or leather, often permanently - the opposite of the desired effect! Try a color remover on these bleach-sensitive garments instead.