LONGVIEW, Wash. - Your bed may be the last place you would expect to find mold but it can happen.

Dan and Cheryl Stokes were shocked to find mold growing inside their bed when they unzipped the mattress and flipped the foam pad.

The Stokes never thought to look until Cheryl's co-worker found mold in her mattress.  Both happen to have Sleep Number beds by Select Comfort, one of the only beds on the market that you can actually open up and look inside.

When KATU asked about the problem, the company said:

Mold can develop in any upholstered product, including mattresses, particularly in humid climates such as Portland.  But, it is rare.  There is absolutely no evidence that mold occurs more frequently in a Sleep Number bed than other mattresses and upholstered products.

In addition, Select Comfort said it improved the anti-microbial agent used to treat Sleep Number beds in 2005 and has not had any complaints since.

Dr. Fred Berman with Oregon Health & Science University said it is true that mold can occur in any mattress if the conditions are right.

"There's moisture and there's humidity coming out of your body when you're sleeping," he said.  "If it's maintained in there, you'll get mold growth."

Of course, you can't see inside a traditional mattress.  Without cutting it open, the best you can do is give it the sniff test.  If it smells musty, you could have mold.

Berman said another hint is if you have unexplained health problems like headaches or a runny nose.

If you have an older Sleep Number bed and find mold inside, Select Comfort told KATU News they would issue replacement parts or give a full refund.  Just call (800) 472-7185.