Volume 96, Issue 6 , Pages 1010-1012, December 1995
Removal of mite allergens from blankets: Comparison of dry cleaning and hot water washing☆☆☆★
Article Outline
Allergy to house dust allergens is common among patients with bronchial asthma and allergic rhinitis. Two species of Dermatophagoides mite, D. pteronyssinus and D. farinae, are important sources of house dust allergens. Two groups of major allergens, Der 1 and Der 2, have been purified from each Dermatophagoides species.1 Immunoassays to measure the Der 1 and Der 2 levels have been used in studies of the level of mite allergens in indoor environments.1
We previously reported that dust specimens obtained from bedding had more mite allergens per weight of dust than those from floors,2 indicating that bedding may be a major reservoir of mite allergens. Because a great portion of our lifetime is spent in bed, it is important to reduce the allergen concentration in bedding.
Blankets are a part of bedding. McDonald and Tovey3 reported that dry cleaning of blankets did not reduce the allergen content in the dust, whereas Vandenhave et al.4 reported that dry cleaning reduced mite allergens and was an effective means for reducing the mite allergen level. In these studies the dust in blankets was collected with a vacuum cleaner before and after washing, and mite allergen levels in the dust extract were measured.
In this study we compared the removal of mite allergens from blankets by dry cleaning with that by hot water washing. A blanket was cut into halves for dry cleaning and wet washing, respectively. Material from six spots on each half of the blanket were collected before and after washing, and mite allergen levels per gram of material were measured; we then compared the effects of dry cleaning and wet washing on allergen removal.
METHODS
Dry cleaning and washing procedures
Dry cleaning was conducted in a large laundry in Japan. Blanket material was steeped with perchloroethylene and detergent, spun, and dried. For wet washing, we used a home washing machine (KW-70R3; Hitachi Ltd., Tokyo, Japan), which has a capacity of up to 7 kg and is equipped with a washing program for blankets: wash cycle (76 minutes) and two rinse cycles (5 minutes each). A soap solution (Akuron; Lion Co., Tokyo, Japan) was added to hot water (55° C) for washing.
Extraction of allergens from blankets
Six blankets, which had been used for more than 1 year, were selected for use in this study. The blankets were about the same size (about 140 × 200 cm) and thickness (about 10 mm). The weight of blankets ranged from 1179 to 1606 gm (mean ± SD, 1420 ± 153 gm). All the blankets were made of acrylic fiber. Each blanket was cut into halves. Before and after washing, pieces (20 mm diameter) of material from six spots were removed with a large puncher. Each piece of material was weighed and immersed overnight in 25 times its weight of phosphate-buffered saline solution containing 0.1% bovine serum albumin and 0.05% Tween-20. The extracts were centrifuged, and the supernatants were stored at −30° C.
Measurement of Der 1 and Der 2 levels
Der p 1, Der f 1, and Der 2 allergens were quantified by a fluorometric sandwich ELISA as previously described.5
RESULTS AND DISCUSSION
The levels of Der 1 in the six blankets (A to F) ranged from 57.2 to 681 ng/gm of material (geometric mean, 162 ng/gm of material) (data not shown). The levels of Der 2 in the blankets ranged from 48.3 to 359 ng/gm of material (geometric mean, 124 ng/gm of material) (data not shown). The ratio of Der 1 to Der 2 in blanket samples ranged from 2:1 to 1:2. This result demonstrated that Der 2 allergen in blankets was as abundant as Der 1 allergen.
Fig. 1, A, shows Der 1 allergen levels in 1 gm of material before and after washing. Washing in hot water reduced the levels of Der 1 in the blankets by more than 95% (mean ± SD, 97% ± 1.0%). However, dry cleaning reduced the levels of Der 1 by 52% to 86% (mean ± SD, 69% ± 13%). The reduction of the level of Der 1 by hot water washing was significantly greater than that by dry cleaning (p < 0.05, Wilcoxon signed-rank test).
FIG. 1.
Mite allergen levels in six blankets before and after washing. Allergen levels are expressed as nanograms per gram of material. The value is geometric mean of six spots in each half of a blanket. There was no difference in the mean levels of allergens between the two halves of the same blanket before washing. A, Der 1, B, Der 2.
Fig 1, B, shows Der 2 allergen in 1 gm of material before and after washing. The reduction of the level of Der 2 by hot water washing ranged from 85% to 96% (mean ± SD, 91% ± 4.1%). In contrast, the reduction of the allergen by dry cleaning varied from 29% to 84% (mean ± SD, 54% ± 24%). The reduction of Der 2 by hot water washing was again significantly greater than that by dry cleaning (p < 0.05). The reduction rate of Der 2 in blankets appeared lower than that of Der 1. Der 1 allergen is associated with mite feces, but Der 2 allergen is associated with mite bodies rather than feces.1 Der 2 allergen might be less extractable from mite bodies than Der 1 allergen from feces.
In this study we found that dry cleaning reduced Der 1 by about 70%, whereas washing in hot water reduced the allergen by more than 95%. Washing in water reduced the Der 2 by 91%. Water washing at 55° C is effective in killing mites and removing mite allergen.1 Large-sized washing machines may facilitate regular washing of blankets at a low cost at home. Frequent washing of blankets in hot water may be beneficial for patients with mite allergy.
References
- . Dust mite allergens and asthma: report of a second international workshop. J ALLERGY CLIN IMMUNOL. 1992;89:1046–1060
- . Measurement of allergens associated with dust mite allergy. II. Concentrations of airborne mite allergens (Der I and Der II) in the houses. Int Arch Allergy Appl Immunol. 1989;90:190–193
- . The role of water temperature and laundry procedures in reducing house dust mite populations and allergen content of bedding. J ALLERGY CLIN IMMUNOL. 1992;90:599–608
- . Effect of dry cleaning on mite allergen levels in blankets. Allergy. 1993;48:264–266
- Airborne cat (Fel d I), dog (Can f I), and mite (Der I and Der II) allergen levels in the homes of Japan. J ALLERGY CLIN IMMUNOL. 1993;92:797–802
☆ From aDepartment of Human Ecology, University of Tokyo; b Department of Epidemiology, National Institute of Health, Tokyo; cDepartment of Medical Technology, Kyorin University, Hachioji; dHitachi Lifestyle Research Center, Tokyo; eRegional Environment Division, National Institute for Environmental Studies, Tsukuba; and fClinical Research Center for Allergy and Rheumatology, National Sagamihara Hospital, Sagamihara.
☆☆ Reprint requests: Masahiro Sakaguchi, PhD, National Institute of Health, Toyama 1-23-1, Shinjuku-ku, Tokyo 162, Japan.
★ 1/54/66380
PII: S0091-6749(95)70244-X
© 1995 Published by Elsevier Inc.
Volume 96, Issue 6 , Pages 1010-1012, December 1995
