INTRODUCTION
Allergic rhinitis (AR) is a common allergic disease in childhood, and
its prevalence is increasing worldwide.1-3 AR
significantly impacts the quality of life by causing various problems,
such as sleep disturbance, emotional stress and impairment of school
activities.4 More importantly, AR is a risk factor for
asthma as “one airway, one disease”.5-7 The
International Study of Asthma and Allergies in Childhood (ISAAC)
employed standardized methodology and showed clearly that the prevalence
of AR increased during childhood, i.e., from 6-7 y.o. to 13-14
y.o.8
However, the onset of AR in children is not well understood due to the
absence of definitive diagnostic criteria. We previously reported that,
in school children with asthma, AR started even before 3 years of
age.9 In the PARIS birth cohort study, the prevalence
of AR-like symptoms was 9.1% at 18 months of age.10However, in the above studies, diagnosis of AR was based only on the
parents’ recall in the former and a symptom questionnaire in the latter.
In addition, those reports did not provide a good description of the
development process.
With the aim of improving our understanding of the onset of AR, we
designed and carried out a high-risk infant cohort study, the Impact of
Allergic Rhinitis on Atopic March (IRAM) in children. Infants less than
2 years of age who had food allergy or atopic dermatitis were recruited
into the study. We prospectively followed up not only their nasal
symptoms, but also their nasal cytology and allergic sensitization for 2
years. The ARIA guidelines classify AR as intermittent or persistent,
not seasonal or perennial.11 However, Japan is
characterized by sole high morbidity of seasonal AR due to Japanese
cedar pollen and a high prevalence of perennial AR due to house dust
mite (HDM). Accordingly, the Japanese guidelines include classifications
for seasonal AR and perennial AR.12 Here, in light of
the relatively late development of pollen sensitization in young
children,13 we focused on development of
HDM-sensitized perennial AR in infancy.