Sure, you want to protect your investment, and mattress and pillow covers do just that. They encase the bedding to protect against allergens, body fluids and bed bugs.Before you start shopping, here's what you need to know, depending on what you need.

If you need a waterproof cover:

In many cases, you get what you pay for in mattress and pillow protection. Very inexpensive, waterproof, plastic covers are available to keep your mattress and pillows dry, but you may pay the price in noisy (crackly) and uncomfortable bedding if your cover moves every time you do. Also, some cheaper plastic and vinyl covers contain chemicals that produce noxious gases you can smell when you open the package. For the safest and most comfortable protection against wetness,  look for well-fitted, cotton mattress covers made with a thin, non-toxic layer of waterproof material. A well-fitted, waterproof cover that completely encases your pillow or mattress can also help keep your bed free of allergens.

If you need an allergy-proof cover:

Dust mites, a common cause of allergies in the home, feed on skin cells that are shed from both humans and animals and are inevitably left behind on any bedding where you or your pet sleep. Special pillow and mattress covers designed for allergy control can help keep dust mites and other allergens to a minimum. Allergy covers should routinely be vacuumed with a hard-edge vacuum cleaner attachment or wiped  with a damp cloth or sponge and allowed to dry thoroughly before being covered with a sheet or pillowcase. Researchers at The University of Edinburgh Medical School found that while using impermeable bedding is one of several ways to reduce dust mite allergy symptoms, it is not usually sufficient on its own and most likely needs to be used along with HEPA air filters and other dust mite repellents for complete control.

If you need a bed bug-proof cover:
If bed bugs are a potential problem, you need a cover that completely encases your mattress, with no tears or other openings. If your mattress sits on a box spring, you must cover that, too. The cover should be made of high-quality, strong cloth that won't tear. Avoid covers with folded fabric over the zipper, because bed bugs can easily hide in the folds. If there's even the tiniest opening where the zipper begins or ends, or anywhere in the cover, sew it up or seal it with duct tape. Bed bugs are very small and can get into your mattress through even the tiniest gaps and holes.

 

Sources:

Indiana University: Preventing a Bed Bug Infestation Web. 5 May 2011.
http://www.ehs.indiana.edu/BedBugs/prevention.shtml

Sheikh A, et al. "House Dust Mite Avoidance Measures for Perennial Allergic Rhinitis." Cochrane Database of Systematic Reviews. 2010 Jul 7;(7):CD001563. Web. 5 May 2011.
http://www.ncbi.nlm.nih.gov/pubmed/20614426