Clinical and E.xperimental Allergy. 1991, Volume 21, pages 39-47 ADONIS t)y6O2l7i:iy|OtH)O7L Clinical evaluation ofa double-blind dust-mite avoidance trial with mite-allergic rhinitic patients F. M. KNIEST, E. YOUNG, M. C. G. VAN PRAAG, H. VOS, HELIANTHE S. M. KORT, W. J. KOERS. FREDERIKE DE MAAT-BLEEKER and JOHANNA E. M. H. VAN BRONSWUK Interuniversity Task Group 'Home and Health', Utrecht State University. Utrecht. The Netherlands Summary Inheritance and allergen exposure are key factors in the development and the course of atopic allergy, expressed as conjunctivitis, rhinitis, asthma or dermatitis. This study concerns the clinical significance of mite and mite-allergen avoidance measures based on intensive cleaning with acaricide (solidified benzylbenzoate) added (10 dwellings), and without biocidal activity (10 other homes) as a control in a double-blind trial with matched pairs. Twenty subjects with persisting rhinitic complaints were selected. They lived in 20 different dwellings and were all sensitized to pyroglyphid mites; 12 ofthem were also sensitized to stored product mites (Acari), Daily symptoms and medication score, guanine and dust exposure, total and mite-specific IgE in serum, eosinophiiia in the blood and in the nasal smear, intracutaneous tests with house dust mite and storage mite extracts were compared in both pairs and groups. Acarologicaldata. physiochemi- cal aspects and exposure assessment are discussed in detail elsewhere. Symptom scores dropped significantly, as did the total IgE and exposure to dust and mite products in the acaricidal cleaner treatment group. After I year, the daily symptoms median was 47% (p = 0-025), total IgE was 38% {P = 00049), and exposure to dust and mite products (guanine exposure) was 53% (P = 0-0449) better or lower than in the controls. Intensive cleaning, without acaricidal treatment performed twice a year, resulted in clinical improvement in four out of 10 subjects, of whom none became free of complaints. In the Acarosan treatment group (cleaning + benzytbenzoate) eight out of 10 subjects improved, in three cases subjective symptoms disappeared. The conclusion is that mite avoidance in homes can be carried out successfully with a special acaricidal cleaning formulation Acarosan. Clinical and Experimental Allergy, Vol. 21. pp. 39-47. Submitted 21 March 1990; revised 5 July 1990; accepted 17 July 1990. Introduction In atopic allergy an inherited constitution is combined with a sensitization towards inhalant allergens in a long- term extensive allergen exposure. In dwellings, a variety of posible allergens may be formed by mites, pets, fungi, insects, etc. [1]. At least 5% of the population (18 million West-Europeans and 11 million North Americans) suffer from such an illness induced by house dust mites [2,3]. Although chronic rhinitis is sometimes thought to be a trivial illness, the morbidity and economic burdens associated with it are immense [4]. Rhinitis is the most Correspondence: Dr F. M. Kniest, GHF, Rheinallee 96, D-6500 Mainz, Germany. common of allergic diseases, even more common than asthma, the infliction most investigated in avoidance studies. Avoidance of ailergens by removing home textiles and padded furniture proved an effective solution in some open and a few controlled dust-mite avoidance studies with atopic patients showing signs of conjunctivitis, rhinitis or asthma. This concept (allergological sanitation or dust avoidance) has been used for decades. Us disadvantage is the unwanted change in living comfort [5.6]. Recently, Platts-lVlills et al, [7] demonstrated a dramatic drop in clinical symptoms after moving asth- matic patients from their dwellings (13 600 ng Der p\ antigen/g dust) to 'dust free' hospital rooms (240 ng Der 39