Repeated antigen challenge in patients with perennial allergic rhinitis to house dust mites

Background: In allergic rhinitis, antigen-antibody reactions occur in the nasal mucosa through antigen exposure. A strong reaction occurs following exposure to a large amount of antigen, whereas no reaction occurs in the absence of antigens. In seasonal allergic rhinitis, nasal hypersensitivity increases during the pollen-dispersing season, which is known as the 'priming effect'. The purpose of the present study was to clarify whether repeated nasal challenges bring about increased nasal hypersensitivity in patients with perennial allergic rhinitis. Methods: Fourteen patients with perennial allergic rhinitis to house dust mites were enrolled in the present study. Repeated challenge tests were performed once daily for 8 consecutive days with a fixed amount of antigen. Results: Sneezing and nasal secretion were slightly enhanced by repeated challenges only on the 2nd and 3rd days, whereas nasal resistance remained unchanged. Increased sneezing and nasal secretion was marked in a group of subjects who were not sneezing at the first challenge, whereas changes in nasal reaction following repeated challenge were less obvious in subjects who were sneezing at the first challenge. Conclusions: In contrast with pollinosis, nasal provocation reactions were not clearly enhanced by repeated provocation. To further understand nasal reactions induced by antigen challenge, studies should be performed under specified conditions (i.e. in an experimental room) with a prescribed quantity of antigens administered, as well as within a study environment