Dust Mite Pillow What Is The Most Important Thing To Look For When Buying Anti Dust Mite Mattress And Pillow Covers?

What is the most important thing to look for when buying anti dust mite mattress and pillow covers? - dust mite pillow

I was there by my doctor that I am allergic to dust mites and should inform the mattress and pillow cover, there are so many products that try to find the best one and why?