Mildew thrives in moist places, so if you leave your sheets or towels in the washer for too long -- or if they stay wet for any other reason -- don't be surprised to find green, brown or even white mildew spots. If left untreated, the mildew will only spread farther onto the fabric. You don't have to toss out your mildew-stained towels or sheets just yet, though. You can remove mildew from sheets and towels safely and quickly with the right products and methods.
Take the affected towels and sheets outside. Use a stiff scrub brush to brush off the loose mildew. It's best to do this outdoors so mold spores aren't released inside of your home. If the fabric is wet, lay it outside in the sun to dry completely before brushing the mildew off. The sun will naturally inhibit mold, but if you can't dry the items outside, let them air dry indoors.
Put the affected sheets and towels into a bucket. Pour undiluted all-fabric bleach over the items so the mildew spots are completely immersed in the bleach. Let the sheets and towels sit in the bucket of bleach for 30 minutes.
Take the items out, wring them out lightly so they're not dripping wet and rinse them out under cool water. Launder the sheets and towels as usual. Let them air dry rather than putting them in the clothes dryer to make sure no mildew is left on the fabric. Putting the items in the dryer while mildew is still present will just make removal more difficult.
Rinse out the bucket well and fill it with a mixture of borax powder and water if the mildew is still there. Use 2 cups of borax powder for every 2 quarts of water. Put the sheets and towels into the mixture so they're completely covered, then let them soak for a few hours. Take them out and launder the sheets and towels as usual.