Mite penetration of different types of material claimed as mite proof by the Siriraj chamber method.

BACKGROUND There are different materials and principles used in the construction of bed encasings. Although these covers claim to have antimite properties, they might not be mite proof. OBJECTIVE This study evaluated the effectiveness of mite penetration of these covers by using the Siriraj chamber method. METHODS Thirty-two covers collected from 9 different countries were categorized according to the materials used to manufacture them. They were (1) tightly woven, (2) film or membrane coated and loosely woven, (3) acaricidal coated and loosely woven, (4) nonwoven, (5) film coated and nonwoven, (6) acaricidal coated and nonwoven, and (7) plastic. Adult mites, Dermatophagoides pteronyssinus, were placed on either the outer or inner surfaces of each of the test fabrics for 3 replications, resulting in a total of 6 samples per fabric. All samples were observed for penetration every day for 1 week under a stereomicroscope. If a single mite penetrated any fabric, it was scored as a penetration. RESULTS Mites penetrated (1) into all samples of film-coated woven and nonwoven covers, an acaricide-coated nonwoven cover, and nonwoven types; (2) from both sides and colonized within the matrix of some samples; and (3) completely in other cases. All of the woven covers and the plastic cover prevented mite penetration. Photomicrographs documented all penetrations. CONCLUSIONS Tightly woven covers and plastic prevent mite penetration, whereas nonwoven, loosely woven, acaricide-coated, and laminated materials do not. The Siriraj chamber method adequately evaluates the effectiveness of antimite barriers. CLINICAL IMPLICATIONS For mite avoidance, allergists should recommend the use of tightly woven covers on suspected bedding containing dust mites.