Evaluation of materials used for bedding encasement: Effect of pore size in blocking cat and dust mite allergen

Background: Mattress and pillow encasings are recommended for patients allergic to dust mites. Many encasements block allergen and are vapor permeable but do not allow free passage of air through the material. Recently, breathable fabrics made from tightly woven synthetic fibers or nonwoven synthetics have been recommend as encasements. Objective: The purpose of this study was to develop a method for testing encasement materials made of breathable fabrics. Methods: Dust samples containing a known quantity of allergen (Der f 1, Der p 1, and Fel d 1) were pulled across a variety of fabrics using a modified dust trap. Airflow through the dust trap was controlled with a vacuum pump. Five minutes after dust was introduced, the pump was shut off. A filter located downstream of the fabric collected allergen passing through the fabric during the test and was assayed with ELISA for the relevant allergen. Fabrics to be tested were obtained from manufacturers and specialty catalogs. Results: As the average pore size decreases, the airflow through a fabric becomes restricted, and the pressure differential created by the vacuum pump increases. Dust mite allergens (Der f 1 and Der p 1) were blocked below detectable limits by fabrics of less than 10 μm in pore size. Fabrics with an average pore size of 6 μm or less blocked cat allergen (Fel d 1). Conclusion: The method we developed provided a rigorous and reliable test for leakage of common indoor allergens through breathable barrier fabrics. Our results show that tightly woven fabrics and nonwoven synthetic fabrics can block common indoor allergens but still allow airflow. (J Allergy Clin Immunol 1999;103:227-31.)