I apologize in advance for mentioning that the human body loses at least a pint of moisture through the skin pores and mouth every night on average.  Our bodies also shed millions of skin flakes.  These two factors in an unprotected mattress combine to make the perfect breeding ground for bacteria and dust mites. 

 

The majority of mission apartments are actually fairly clean, but most missions now recommend taking a matress cover.

 

This isn't just a plastic bag to put over your mattress (that might work, but you would sweat like crazy and the mattress would rot and mold over since it couldn't breathe.  The Protect-A-Bed® mattress protector offers the unique Miracle Membrane® with the Total Heat Transference Formula.  This means that while it is waterproof on the top and does not allow dust mites or allergens through, it does breath. 

Protect-A-Bed® Mattress Protectors Are:
Guaranteed to moderate temperature and enhance sleeping comfort
Waterproof yet air vapor porous - acting the same way as human skin
Effective in preventing bacteria and dust mites from breeding in your pillow and mattress (a major cause of asthma, eczema and rhinitis)
Protects mattresses from stains (accidental spills, perspiration, bodily fluids)
Machine washable on hot, tumble dry medium
Especially helpful in cases of incontinence
Ultra thin with four-way stretch does not detract from the comfort of the mattress
Can be used on all visco elastic, inner spring and latex mattresses
High Quality Fitted-sheet style
Expandable skirt ensures mattress protector fits any depth of mattress (8" to 20")
Wash durability rating: > 200 washes
Soft and super absorbent
Can be sterilized at 50° C/120° F
Tested for harmful substances according to Oeko-Tex Standard 100

Has the Good Housekeeping seal of approval

Has a 3 year warranty against defects in workmanship or materials