The best way to protect any futon mattress is to buy a futon cover. There are so many beautiful futon covers made that picking the right style will be a hard decision. Another consideration is the size of the cover. The most common sized futon cover is a full size, which measures 54' x 75'. The thickness of most futon mattress can vary, but the most common thickness is 6' to 8' thick. Most futon covers will fit futon mattresses that are 6' to 8' thick. A queen futon cover is 60' x 80', and is much more uncommon. In fact, most people that order queen futon covers end up returning them for full size covers. So, it's a good idea to measure your futon mattress, even if you think it's a queen, just to make sure.
The first consideration will be whether to buy a washable cover, a dry clean only cover, or a spot clean only cover. If you have children or pets, a washable cover is the best choice. Always refer to the manufacturers tag and follow their instructions for cleaning or washing your cover. Generally most washable futon covers should be washed either by hand, or in a washing machine on gentle, and with cold water using a mild detergent. You can also hand wash futon covers in the sink using woolite, or another gentle detergent. After washing and rinsing, the cover should be line dried, or tumble dried in a dryer, on cool temperature.
Great care should be taken not to wash your cover in warm or hot water, and especially not to dry your cover in the dryer on warm or hot heat. This will no doubt cause shrinkage, and chances are your cover will not fit your mattress and will be ruined. If you've lost the tag on your futon cover, try to contact the dealer you purchased the cover from to see if they have a record of the cover you purchased, and can put you in contact with the manufacturer to find out what the cleaning instructions were.
Some covers are made for dry cleaning only which can be expensive and many people are chemically sensitive, and try to stay away from the chemicals used in dry cleaning. Some futon covers are meant to be spot cleaned with a mild detergent and then blotted with a towel.
There are many vinyl or leather looking futon covers. These covers are great for people with pets or small children, and they can simply be wiped off with a damp cloth or sponge. The disadvantage is that they can be hot or sticky to sit on.
Sunbrella covers are the most incredible covers of all. They are sun fade resistant, and water resistant. To clean them you basically brush off the dirt. You can wipe them off with a sponge with a mild detergent, or wash them, and you can even use bleach on them and they won't fade. They are actually guaranteed to not fade for 5 years in the direct sun.
The following statement is something that you should do AT YOUR OWN RISK. In our store, when a futon cover got stained or soiled, we never took it to the dry cleaners. We always took them home, and washed them in the sink in slightly warm water, with some Woolite, and then rinsed them off a few times, and then stretched them out flat, and let them dry on some large towels on the floor. This worked every time except once, when the cover shrunk badly. Actually the width stayed the same, but the length shrunk about 1 Foot. We threw that one away! The rest of the covers that were supposed to be dry clean only, or spot clean only, washed up perfectly.