Sensitization to indoor allergens like house-dust mite and animal dander as well as outdoor allergens like grass and tree pollen play an important role in the development to atopic airway disease, i.e. atopic rhinitis and conjunctivitis and allergic asthma. Studies on emergency room patients in the US showed that the sensitization to cat dander and house-dust mite Dermatophagoides represented risk factors for acute attacks of asthma. However, irrespective of the inheritance of atopy, disease of specific organs and expression of symptoms remain highly variable and are likely to depend on a multiplicity of environmental factors, the most important of which is likely to be the level of exposure to the sensitizing allergen. There is increasing evidence that exposure to potential allergens early in life is important. Concentrations and timing of the exposure seem fundamental. The elimination of allergens in households of atopic individuals is crucial in a prophylaxis and therapy. There have been several publications on mite allergen elimination procedures; a lot of them are uncontrolled, and allergen reduction is not significant. This article tries to compare trials reporting of improvement of clinical symptoms and significant reduction of indoor allergens with those trials which did not achieve significant results.