Remove the pillowcases from the pillow if necessary.
Mix together equal parts white vinegar and warm water in a basin or sink.
Place the pillowcases in the liquid and allow them to soak for 30 minutes.
Launder the pillowcases according to their directions. You can wash most cotton or cotton-blend pillowcases, for example, on the gentle cycle in your washer with a mild detergent. These pillowcases are usually safe to dry on low heat, although you should refer to the instructions just to be safe. Wash silk pillowcases by hand with a mild detergent. Dry them in a warm area that is out of the sun, since the sun's light can fade the color of the silk.