Manchester Asthma and Allergy Study: Low-allergen environment can be achieved and maintained during pregnancy and in early life

Background: Early exposure to dust mite allergens may be critical for prima ry sensitization. Reducing exposure may offer a realistic chance for primar y prevention of sensitization and asthma, but it is essential to implement measures that can achieve and maintain the low-allergen environment. Object ive: Our purpose was to assess the effectiveness of mite allergen avoidance measures in achieving and maintaining a low-allergen environment during pr egnancy and in the first year of life. Methods: The Manchester Asthma and Allergy Study is a prospective, prenatal ly randomized study that follows the development of asthma and atopy in a c ohort of infants at high risk (both parents atopic) who are randomly alloca ted to full mite allergen avoidance or to a normal regimen. Avoidance measu res comprise (1) mite-proof covers (mattress, pillow, and quilt) for parent al bed, (2) high-filtration vacuum cleaner, (3) vinyl flooring in infant's bedroom, (4) new crib and portable crib mattresses encased in mite-proof ma terial, (5) benzyl benzoate (Acarosan) applied on carpets and soft furnitur e, (6) bed linens washed in hot water weekly, and (7) washable soft toys. D ust samples from the parental bed, bedroom floor, living room floor, infant 's mattress, and nursery floor were collected between the 10th and 14th wee ks of pregnancy, immediately after birth, and then at age 6 months and 1 ye ar, and Der p 1 levels were determined by mAb-based ELISA. Results: Recovered Der p 1 from maternal mattress was reduced by 97.25% (95 % confidence interval [CI] 95.25%-98.41%) during the second and third trime sters of pregnancy, with the effect persisting for 6 months (98% reduction, 95% CI 97.258-99.1%) and 12 months (97.6% reduction, 95% CI 95.7%-98.6%) a fter the birth (active vs control, P <.000001). Total Der p 1 from bedroom floor in the active group was reduced by 53.7% (95 % CI 25.7%-71.2%) in sam ples collected within 4 weeks of the child's birth, with the percentage red uction being 62.8% (95 % CI 39.3%-77.2%) at 6 months and 26.5% (95% CI-24% to 57.1%) at 1 year (active compared vs control, P <.007). Der p 1 levels i n crib mattress and nursery floor in the active group were extremely low (c rib mattresses geometric mean [95% CI] 2.3 ng [1.6-3.4] at birth, 6.8 ng [4 .5-10] at age 6 months, and 15.6 ng [9.8-24.8] at age 1 year [active vs con trol, P =.001]; nursery 1 ng [0.9-1.1] at birth, 1.7 ng [1.2-2.5] at age 6 months, and 2 ng [1.3-3.5] at age 1 year [active vs control, P <.00001]). T he total amount of allergen recovered at age 1 year was 29-fold (95% CI 15. 1- to 56.7-fold) higher in the control group than in the active group. Conclusions: The avoidance measures used in this study achieved and maintai ned a low mite allergen environment during pregnancy and in the first year of life in homes of infants at risk of atopy.