Short answer
Mite-impermeable encasings are woven so tightly that bed mite allergen can't pass while air and water vapor can. The allergist practice parameter says woven microfiber fabric with a mean pore size under 10 microns can block the main mite allergen, Der p 1, and recommends woven over nonwoven encasings. In a randomized trial in mite-sensitized children with asthma, encasings cut the risk of emergency hospital attendance by 45%.
Key terms used on this page
- Encasing pore size:
- The average gap between fibers in an encasing fabric. The practice parameter says under 10 microns blocks the main mite allergen and under 6 microns blocks cat allergen.
- Woven microfiber encasing:
- A breathable zippered cover made of tightly woven ultrathin filaments that filter allergen. The practice parameter prefers it over nonwoven covers, which can't be washed.
- Mite-impermeable encasing:
- A zippered cover that fully encloses a mattress, box spring or pillow so mite allergen can't pass through. The practice parameter says woven microfiber with a mean pore size smaller than 10 micrometers can block Der p 1, and it does not recommend nonwoven covers.
<10 µ
Pore size
Woven microfiber fabric with a mean pore size under 10 microns can block passage of the main bed mite allergen, Der p 1.
45%
Lower risk
In a randomized trial of 284 mite-sensitized children with asthma, the risk of emergency hospital attendance was 45% lower with mite-impermeable bed encasings.
An allergen encasing works by fabric structure, not by a waterproof film.
General information about mattress care, not medical advice. For allergy or asthma questions, talk with your doctor.
Pore size
The practice parameter: "Woven microfiber fabrics with a mean pore size smaller than 10 µ can effectively block passage of Der p 1, whereas a mean pore size smaller than 6 µ is necessary to block cat allergen Fel d 1." Those fabrics "prevent mite allergen escape yet allow air and water vapor to pass freely." See encasing pore size and woven microfiber encasing.
Woven, not nonwoven
The same paper notes that nonwoven encasings "trap mite allergens and are not washable, leading to allergen accumulation." Choose woven.
The evidence
In Murray et al. (2017), 284 mite-sensitized children with asthma were randomized to mite-impermeable or placebo encasings. The risk of emergency hospital attendance was 45% lower in the encasing group.
Encasing plus sanitation
An encasing contains allergen inside the mattress; it doesn't remove what's there. See can sanitation replace an encasement? and our bed mites hub.
Sleep Sanitation's view
This section is our view. Sleep Sanitation serves Omaha, Lincoln and surrounding towns. Every visit includes dry vapor steam, HEPA vacuuming, UV-C light treatment, the built-in bed mite sensor on our JIGOO UV-C mattress vacuum and a moisture check before we leave. We take your protector off at the start of the visit, so you don't need to strip it first; wash it yourself per its care label while we work or afterward. The first mattress is $249. Call or text (402) 512-5658, or email info@sleepsanitation.com. Office hours are Monday to Friday, 9 to 6, and we return calls and texts on weekends.
Changelog
- 15 October 2026: First published. Sources accessed on this date.
Sources
- Environmental Assessment and Exposure Control of Dust Mites: A Practice Parameter (Portnoy et al., 2013) · PubMed Central (Annals of Allergy, Asthma & Immunology)
- Preventing Severe Asthma Exacerbations in Children: A Randomized Trial of Mite-Impermeable Bedcovers (Murray et al., 2017) · PubMed (American Journal of Respiratory and Critical Care Medicine)
- Dust Mites and Cockroaches · National Institute of Environmental Health Sciences
Last reviewed October 15, 2026. Manufacturer specifications and care instructions change; check the current version for your exact model. This page is general information, not medical advice. How we source and check pages: editorial standards.