Asthma in Patients With Japanese Cedar Pollinosis

Japanese cedar pollen is the most common causative allergen for seasonal allergic rhinitis (AR) in Japan. More commonly known as Japanese cedar pollinosis, it occurs in spring causing the typical symptoms of seasonal AR, such as sneezing, rhinorrhea, nasal obstruction, nasal itching, and itching of the eyes. Previous reports indicate that the prevalence of Japanese cedar pollinosis among Japanese was 26.5%. According to a more recent questionnaire-based survey, the prevalence of Japanese cedar pollinosis in patients with adult asthma might be up to 30% to 50%, suggesting higher rates than that previously reported. Moreover, 30% to 60% of adult asthmatic patients with concomitant pollinosis have exacerbations of their asthma symptoms during the Japanese cedar pollen season. These findings suggest that concomitant Japanese cedar pollinosis may be an aggravating factor in patients with asthma. As with other pollens, such as grass and birch, Japanese cedar pollen was shown to be a trigger factor for worsening asthma. In clinical practice, a number of Japanese patients with asthma are monosensitized to Japanese cedar pollen but not to other antigens. Further studies are needed to elucidate the mechanisms of Japanese cedar pollen in inducing and in exacerbating asthma. The presence of concomitant AR is often associated with the difficulty in asthma control. However, there has been a controversy whether treating concomitant AR by intranasal corticosteroid would produce better asthma-related outcomes in patients with asthma and AR. The effect of treating concomitant cedar pollinosis by intranasal corticosteroids on asthma control in patients with asthma and cedar pollinosis also remains unknown. Certain systemic treatments, such as leukotriene receptor antagonist and anti-IgE monoclonal antibody, are supposed to reduce the symptoms of both asthma and AR in patients with asthma and concomitant AR. In conclusion, Japanese cedar pollinosis is often associated with exacerbations of asthma. Further investigations are expected to elucidate the precise impact and mechanisms of Japanese cedar pollinosis in asthma.