The most important principle in the treatment of allergic diseases is to avoid or reduce exposure to the causative antigen. Causative agents that induce allergic diseases or exacerbate symptoms are classified into indoor and outdoor allergens. House dust mites and pet's hair are typical indoor antigens. Air pollution as well as allergens are important deterioration factors, and environmental management is essential for alleviating symptoms of allergic diseases. Therefore, we are about to evaluate the impact of the air cleaner to the allergic rhinitis patients.