House dust mite allergen exposure does not affect exhaled nitric oxide levels in atopic non-asthmatic children

We have recently demonstrated that exhaled nitric oxide (eNO) is elevated in healthy children with positive immunological reactions to common allergens. The mechanism(s) for this finding were unknown but a possible explanation was sub-clinical inflammation caused by allergen exposure. The aim of the present study was to investigate if exposure to house dust mite allergen (Derpl ) was associated with elevated eNO in children with a positive skin prick reaction to Derpl. Twenty-one children (age range 7-12 years; 7 girls) who had previously tested positive to Der p 1 were recruited for the study. House dust mite was collected from the beds of the children by vacuuming the surface of their mattress for 2 minutes. Derpl levels were determined by the Rapid Test for Mite Allergen (Indoor Biotechnology's Inc.). Exhaled NO was measured using a fast response nitric oxide analyser (Seivers NOA280). Eight children had eNO levels >20ppb, 6 had levels between 10 and 20ppb and 7 children had levels <10ppb. The children were grouped according to the level of Der p1 collected from their mattresses (high, medium or low). There was no significant difference for eNO levels between the three groups. Average (Geometric mean (95% confidence intervals) eNO levels were 14.1ppb (9.2-21.8ppb) for children with high levels of Derpl in their mattresses, 16.9ppb (11.1-25.5ppb) for children with medium levels and 18.1 (9.4-35.2) for children with low levels. In conclusion we were unable to find an association between sensitisation, current allergen exposure and eNO levels.