A device is disclosed that provides parasite, dust mite and allergen protection for an encasement used for a mattress or foundation. The device can be part of the original encasement or added as an after-market item to a conventional encasement to prevent the egress of parasites, dust mites and allergens from the gap between the zipper slide and the zipper stop and prevent movement of the zipper slide when the zipper is completely zipped up. The device includes a at least one compressible material that is used. The compressible material is compressed to seal the gap and prevent movement of the zipper slide. In one embodiment of the invention, the device allows the mattress or foundation within the encasement to breathe while blocking parasites, dust mites and allergens from escaping from within the encasement.