A controlled trial of house dust mite eradication using natamycin in homes of patients with atopic dermatitis: effect on clinical status and mite populations

In a controlled clinical trial, patients with atopic dermatitis carried out house dust mite eradication procedures on their mattresses, using natamycin or a matched placebo spray, with or without vacuum cleaning, for 4 months. For the two groups that used vacuum cleaning, mite numbers fell significantly both by comparison of mean initial and final numbers and by calculating mean rates of reduction from regression analyses (P less than 0.01 in all cases). There were no differences between the groups in the magnitude of the decreases. For the two groups that did not use vacuum cleaning, mite populations remained virtually unchanged. These results indicate vacuum cleaning not natamycin had the major effect on mite eradication. Mean symptom scores of patients in all four groups were slightly reduced by the end of the trial, but there was a greater reduction rate (P less than 0.01) in the combined scores of the groups that did not use vacuum cleaning, demonstrating a lack of correlation between improvement in clinical score and lowered mite numbers. No patients entered remission and the maximum improvement in clinical score was only 47%. Natamycin and vacuum cleaning neither alone nor in combination proved valuable in reducing mite numbers sufficiently to provide clinical benefit.