P-122 Abstract: Allergen exposure in childhood is thought as an important determinant for initial sensitization of the immune system and hence subsequent progression to clinical allergic diseases. Meanwhile, children are likely exposed to aeroallergens at higher levels than adults since they breathe the air more proximate to a ground, a potential allergen reservoir such as house dust. To elucidate the disease expression mechanisms, accurate assessments of early life exposures to aeroallergens are essential. The purposes of this study are to: (1) point out a specific nature of children's exposures to aeroallergens; and (2) demonstrate the personal aeroallergen sampler (PAAS), a passive sampler for coarse airborne particles we recently developed, for assessing children's exposures to aeroallergens. To exemplify a specific nature of children's exposures to aeroallergens, the concentrations of resuspended house dust potentially allergenic were monitored at a height of a hypothetical children's breathing zone, i.e., 30 cm height from an artificial dusting point, by a light scattering particle counter, and compared with those at an adult's breathing height, i.e., 120 cm. Meanwhile, the PAAS was developed to assess children's exposures to aeroallergens in the field. The PAAS was designed to collect coarse airborne particles on the horizontal collection surface by gravitational settlings. The collection surface of the sampler is continuously oriented upward by means of a structure resembling a gyroscope to prevent distortion of the measurement results by inclination of the sampler. Experimental results showed higher peak concentrations of resuspended house dust at the children's breathing height during artificial dusting events, suggesting children are likely exposed to a potential risk to inhale concentrated aerosol allergens resuspended by themselves. The tendency was noticeable for larger particles such as those having diameters larger than 5 micrometer. Meanwhile, particle collection velocities of the PAAS were experimentally obtained to apply to the assessments of children's exposures to aeroallergens. Furthermore, airborne fungi, a kind of aeroallergens, collected by the PAAS could be analyzed by an existing cultural procedure to assess personal exposures to those allergen species. The PAAS is suitable for child subjects since it is light (approximately 50 g) and small (5 × 4 × 4 cm). Although existing active samplers are likely impractical for child subjects, the PAAS can be used to assess the allergen exposures of children, which are likely specific as was demonstrated, and hence create opportunities to understand the mechanisms of the disease expressions in early life.