Protective mattess, box spring, duvet and pillow encasings are essential in containing the bed bugs, mites and their harmful allergens.  They also cut off mites food supply as the human skin scales cannot penetrate the encasings.

Fitted versions or quilted pads DO NOT protect you from the dust mite allergens or bed bugs since the mattress is not totally encased and the quilting pattern punctures the fabric resulting in holes large enough for dust mites and bd bugs to escape.

Clinical studies in patients using allergen avoidance measure have shown significant reductions in allergy symptoms, as well as reduction in medication usage.  Studies have shown that there was a 52.3% improvement noted in asthma sufferers using the dust reducing bedding, and a 42.3% improvement amongst allergic rhinitis patients using encasings.

The micron/pore size tells you how much open air space exists between the threads in bedding fabric.  Pore size is the most important factor in determining how effectively allergens are blocked.  Humans don't actually inhale whole dust mites; rather, we breathe in their allergenic waste particles and decomposed body parts, and this what causes allergy symptoms.  Dust mite fecal particles average around 10 microns in diameter (one microm is 1/25,000 of an inch.  To give you an idea of how small this is dust mites are around 300 microns and a grain of sand can be over 800 microns!)
Therefore, in order to effectively block dust mite allergens, the pore size of allergy relief bedding must be smaller then 10 microns.