ABSTRACT
House dust mite allergen appears to be a major cause of allergy and asthma in children and adult. Thus control of house dust mites is necessary. The objective of this study were to investigate the acaricidal activity of Permethrin, a safe and effective insecticide against house dust mites comparing with Benzyl benzoate, an acaricide which has been widely used for control of house dust mite. A safe and effective dose of each chemical as well as their residual efficacy when impregnated on fabrics were determined. The result shown that median lethal concentration (LC50) and 95% lethal concentration (LC95) of Permethrin were 6.98 mg/ft2 and 42.49 mg/ft2 respectively while median lethal concentration (LC50) of Benzyl benzoate was 4.55 mg/ft2 and 95% lethal concentration (LC95) was 27.68 mg/ft2. Studied on the efficacy and persistence of chemicals-impregnated fabrics against house dust mites shown that the potency of Permethrin impregnated fabrics dropped to 50% at the second months while the potency of Benzyl benzoate were gradually dropped to 80%, 60% and 50% in second, third and fourth month accordingly. Chiang Mai Med Bull 2002;41(1):43-50.