A hydrodynamic bearing, a motor including the same, and a recording and reproducing apparatus which can improve vibration resistance property and suppress noises even in a situation where vibration is expected are provided. The invention relates to an allergen-reducing agent containing water and a water-soluble polymer compound having units having hydroxy or carboxy groups wherein at least a part of hydrogen atoms of the hydroxy or carboxy groups are substituted by specific groups containing a polyether group. The arm may include a first threaded portion, and the intermediate member may include a second threaded portion coupled to the first threaded portion. The sorbent structures can be periodically recoated with sorbent while the gas is still flowing. Users can also be registered \u201con the fly.