Exposure to inhaled allergens is a pathogenetic factor in allergic asthma. However, physical, chemical and combined methods aiming to reduce airborne allergen levels have shown little or no effect in reducing asthma symptoms in people who are sensitive to perennial allergens.Aims and objectives: This study aims to investigate treatment with Temperature controled Laminar Airflow (TLA) with a very low particle concentration directed to the breathing zone in subjects with allergic asthma during night sleep. The hypothesis is that the decreased allergen exposure during the night will have an effect on quality of life and bronchial inflammation.