The answer to this depends on the individual mattress protector as some do and some don't. Below we will explain this in more detail. First of all we have to understand how and why dust mites are living inside your mattress.
Why do dust mites live inside a mattress?
Dust mites are very small microscopic creatures that are Arachnids which is the same class as spiders. They are actually part of a sub group of arachnids called acarina which includes mites and ticks. Like every living creature dust mites require food and moisture to survive. Dust mites have evolved to live off the tiny particles of skin that we shed as we go about our lives. When you see dust hanging in the air in a shaft of sunlight this dust is made up of these skin particles as well as other particles. These eventually settle and begin to decompose. It is at this point that dust mites can consume these skin particles. Of course in our homes we are often wiping down and dusting surfaces and vacuuming and sweeping and mopping floors so these particles are in small numbers in these locations. However where we cannot clean easily these particles build up and become home vto the dust mites that feed here.
Your mattress is absolutely perfect for dust mites to live in. As you lie in bed the sheets rub against your skin brushing off those loose flakes, dandruff falls from our heads. During the night these tiny particles are worked down through your sheets into the mattress below. They usually come to a rest a centimetre or two below the surface. We also produce persiration and other moisture during the night, this too ends up soaking into your mattress. This moisture accelerates the decomposition of the skin particles into a form that the dust mites can consume.
It is virtually impossible to remove these dust mites from your mattress once they are there. You can vacuum the mattress which will probably remove some of them, but they are deep enough to avoid most of the suction power and the colony will quickly replace any lost mites. Even beating the mattress will just distribute them around the mattress and the area that you are beating the mattress and again enough will be left to quickly build the colony back up again.
For this reason you need to use the right type of mattress protector to stop the dust mites in the first place or to cut off their food supply if they are already there.
What kind of mattress protector protects against dust mites?
First of all the mattress protector needs a physical barrier to stop the particles from passing through. This essentially means that it needs a waterproof barrier, because you need that anyway to stop any perspiration or moisture from passing through too. If the protector isn't waterproof then those particles of skin will find their way through the individual fibres of the fabric. It doesn't matter how tight the fabric is woven, as you move around and stretch it, those threads part and the particles will work their way through so a waterproof membrane is an absolute must. If the dust mites cannot receive food and moisture they will die, if they continue to receive food and water they will breed and multiply.
But not just any waterproof membrane! You could wrap your mattress in bin bags or cling film and it would then have a waterproof cover on it but it would be incredibly uncomfortable to sleep on, hot sweaty and rustly. No it needs to be a particular kind of waterproof layer. It needs to be comfortable for you to sleep on so it needs to be quiet, soft, breathable and not make you hot and sweaty. So it needs to be made of polyurethane which has all of these properties. The waterproof barrier also stops the dust mites waste products from puffing up out of the mattress as you toss and turn, and consequentially stop you from breathing in these waste products and who wants to breathe in dust mite poo?
What about anti allergy chemically treated non waterproof mattress protectors? Well regardless of the treatment, if they haven't got a waterproof barrier then skin particles and moisture are still going to pass through to the mattress below. the chemical protection will only stop dust mites from living within the fabric of the protector, it will do nothing to stop the dust from living inside your mattress.
What about waterproof mattress protectors that are quilted? Well if they have a waterproof barrier they will stop food and moisture from reaching the dust mites inside the mattress so that is good BUT the quilted section that is sitting above the waterproof barrier will become a new home to dust mites. The waterproof barrier will hold the skin particles in place and the dust mites will live in the quilting and you pretty much have the same problem as you would without a mattress protector. The only difference being that at least you can wash the protector. However that still isn't a full solution because quilted protectors can only be washed at relatively low temperatures that are not high enough to kill dust mites, mould or bacteria. So a quilted waterproof protector is better than no waterproof protector, but nowhere near effective as a non quited waterproof mattress protector.
So which is the best mattress protector to prevent dust mites?
The very best is Allergon, its features are
Waterproof Polyurethane Barrier
Virtually undetectable in use
Can be washed at up to 90c
Can be tumble dried
Dust Mite Proof Barrier
Stops dust mite waste from passing through to you
Efective Dust Mite control
Available in 20 mattress sizes
See Allergon here Allergon The Best Dust Mite Mattress Protector