White bed sheets turn yellow with age and usage because of the skin-care products, lotions, body oils and sweat that work their way between the sheets and cling to its cotton fibers. Adding bleach to the laundry load can yellow them even more because of oxidation and bleach's reaction with your body's fluids.
Nightly Sweat and Body Oils
You can't help it that your body sweats at night when you sleep; it's part of the body's nature to do so. Body sweat, as it dries, is the most common reason white sheets and pillowcases turn yellow, but you may also notice a wet spot near your mouth on the pillow when you wake up. The unmentionable bodily fluids, along with saliva that escapes your mouth during sleep, also causes yellowing bed sheets.
Green Whitening Method
Add 1/2 cup of baking soda -- not bleach -- along with the detergent when you're washing white bed linens during the wash cycle. In place of fabric softener, which actually adds a waxy substance to linens and towels, making them nonabsorbent, pour in a 1/2 cup of vinegar during the rinse cycle. The vinegar smell rinses out, but the vinegar leaves sheets feeling soft when combined with the baking soda in the wash. For an even greater whitening effect, hang white bed linens in the sun to dry, which leaves a naturally fresh smell on the sheets. If they come out a little stiff after drying outside, simply toss them in the dryer on the wrinkle release setting to soften them up.
Top-Load Washer Whitening Method
Fill a top-load washer 1/3 full with hot water, 1 cup of oxygen bleach, 1 cup powdered dishwasher detergent, 1 cup of laundry detergent and 1/2 cup of borax, and agitate the ingredients until they are thoroughly mixed. Add the sheets to the load and finish adding the hot water until full. Allow the machine to go through the wash and rinse cycles. When it is done, set the washer on the rinse cycle one final time. Hang the sheets outside to dry in the sun, softening in the dryer to remove wrinkles or stiffness.
Preventing Yellowed Sheets
Make a natural bleach alternative to use to prevent white sheets from yellowing. Mix together 1-cup hydrogen peroxide, 12 cups of distilled water and 1/4 cup of lemon juice. Add 2 cups of this mixture to the wash load when cleaning sheets. In place of the green bleach method, use an oxygen bleach during regular wash loads. Only wash white sheets and linens in the load; don't add colored items to the mix. Hang outside in the sun to dry on a clothesline, a line that is strung tautly between two T-posts cemented in the ground.