The effects of a single treatment of an acaricide, Acarosan, and a detergent, Metsan, on Der p 1 allergen levels in the carpets and mattresses of asthmatic children.

Baseline levels of the house-dust mite allergen, Der p 1, were measured on the carpets and mattresses of 60 pure-mite-sensitive asthmatic children in the Cape Peninsula, by means of an enzyme-linked immunosorbent assay (ELISA). High levels of mite allergens were recorded (range 2-50 micrograms Der p 1/g dust). In order to investigate the efficacy of the application of acaricides to carpets and bedding, 3 groups of 20 children were studied. Carpets and mattresses in group A were treated with a detergent, Metsan (Snowchem), and in group B with Metsan combined with the acaricide, Acarosan (Noristan). Group C was a control group in which no treatment was applied. The level of airway hyperreactivity (PC20) to histamine was measured at the beginning of the study and again 3 months after acaricide treatment. Significant reductions in carpet Der p 1 levels were achieved in group A (22.83 v. 13.26 micrograms Der p 1/g dust; P = 0.04) and group B (21.76 v. 13.26 micrograms Der p 1/g dust; P = 0.01), but mite levels were not reduced in any of the mattresses treated. There was also no improvement in airway hyperreactivity in any of the groups. This study clearly demonstrates that at present it is not possible to reduce Der p 1 antigen levels in mattresses in the Cape Peninsula with the available acaricides, even when one of these is combined with a detergent solution. Until strategies are developed which will significantly reduce Der p 1 levels in the bedding of sensitive individuals, a reduction in ongoing airway inflammation and airway hyperreactivity cannot be expected.