Hi Missnicole85,
There is more information about the pros and cons of different types of mattress protectors and some examples of each of them in post #89 here that should be helpful.
There is a difference between a mattress protector (which are generally 5 sided and fit over the mattress like a fitted sheet and are easily removed for cleaning) and a mattress allergy (or bed bug) encasement which completely encloses the mattress on all sides and has a zipper to close it off and are much more difficult to remove (and aren’t meant to be removed or cleaned on a regular basis).
I would keep in mind that a mattress encasement that is suitable for bed bugs can prevent bed bugs from infesting your mattress (or escaping your mattress if they are already there) but they won’t prevent a bed bug infestation in your home because bed bugs can hide in many places in your home besides just your mattress.
If you are also looking for a mattress encasement to help protect against dust mites and/or bed bugs then there is also more about dust mites and allergies in post #2 here and there is more information about mattress allergy and bed bug encasements in post #2 here and the posts it links to that can help you choose between different products or combinations of products that best fit your own specific needs and criteria.
Phoenix