Accumulation of house-dust mite (Der-p-1) levels on mattress covers

Mattresses serve as a large reservoir for house-dust mite antigens and harbour the highest mite levels within the household. Mite reduction measures have previously been shown to be unsuccessful. The effect of mattress covers and acaracides on Der-p-1 levels in the mattresses of 60 patients with mite-allergic asthma was studied. Der-p-1 levels were measured using monoclonal antibodies (ELISA method). Baseline levels were recorded and re-assessed at 8-week intervals over a 6-month period. Patients were randomised into three equal groups. In group A mattresses were treated with Metsan (Snowchem) and benzylbenzoate only; group C had their mattresses covered with mattress covers (Allergy Control Products). Group B was the control group. We were unable to demonstrate any reduction of mite levels in the beds of all 3 groups. In fact all 3 groups demonstrated an increase in Der-p-1 levels over the study period, viz. group A (mean pre: 14.28, post: 34.18 micrograms/g dust); group C (mean pre: 8.26, post: 20.80 micrograms/g dust) and group B (mean pre: 18.21, post 38.47 micrograms/g dust). However, 12 patients in group C had their mattress covers washed in hot water at weekly intervals over a 5-week period at the end of the study. The results demonstrated a significant reduction in mite levels (mean pre: 41.95, post: 26.2 micrograms/g dust; P = 0.027). We therefore conclude that the use of mattress covers per se does not reduce Der-p-1 levels. The regular application of benzylbenzoate and Metsan does not prevent the accumulation of Der-p-1 on mattresses either.(ABSTRACT TRUNCATED AT 250 WORDS)