Personal exposure to house dust mite allergen in bed: nasal air sampling and reservoir allergen levels

Background Assessment of personal exposure to dust mite allergen has relied on proxy measures. Only recently has a means to directly measure inhaled allergen particle number become available (the intra-nasal air sampler). Objective To quantify inspired dust mite group 1 and group 2 allergen-bearing particles in bed in undisturbed conditions prior to sleep by nasal air sampling and to investigate the relationship between inhaled particles and reservoir allergen levels. Methods Twelve volunteers wore nasal samplers in bed for 6 evenings, nose-breathing in undisturbed conditions. Allergen-bearing particles ('halos') were detected by immunostaining for Der p 1, Der p 2, or Der p 1 and Der p 2 together, and counted by light microscopy. Count data were square root transformed for analysis of variance. Mattress dust samples were assayed for Der p 1 and Der p 2 concentrations. Results Square root detransformed mean particle counts per 30-min sample were: Der p 1, 4.22; Der p 2, 5.9 Der p 1 + Der p 2. 4.87 and for all samples, 5.01, with no difference between the groups. With replicate samples. halo number correlated significantly with mattress allergen concentrations (Der p 1 r = 0.80, P < 0.01 Der p 2 r = 0.68, P < 0.02). Conclusion Nasal air sampling can be used to quantify nocturnal Der p exposure in undisturbed conditions in an area with moderate exposure to mite allergen and can provide a direct measure of inhaled mite allergen. The choice of either Der p 1 or Der p 2 is appropriate for this purpose.