Introduction
Changes in the prevalence of atopic dermatitis (AD) according to age in
Korean children have been observed. Although the development of AD
during infancy is decreasing, prevalence in late childhood is
increasing, indicating rising rates of late-onset or early-onset
phenotypes (1). AD is a persistent disease with a high burden on
children and their families. In combination with genetic factors,
environmental influence is an important contributor to the pathogenesis
of AD, indicating the importance of early interventions to improve or
prevent AD outcomes(2).
Smoking during pregnancy is a well-established risk factor for adverse
outcomes such as low birth weight (3), spontaneous abortion(4), and
preterm birth (5) and wheezing (6). However, the proportion of active
smokers among pregnant women in Korea is comparatively lower than that
in western countries. A study conducted in South Korea reported that
0.55% of mothers admitted to actively smoking, while 3.03% were
considered to be actively smoking based on their urine cotinine levels
(7).
Approximately 35%, 33%, and 40% of nonsmoking females, males, and
children are exposed to SHS daily (8). In Korea, 60.4% of pregnant
non-smokers reported exposure to SHS during pregnancy(9). The Cohort for
Childhood Origin of Asthma and Allergic diseases (COCOA) study revealed
that prenatal SHS exposure increases susceptibility to lower respiratory
tract infections in infancy(10). Given that AD is a disease affected by
environmental factors, the possibility for SHS to be a potential
contributor could not be ruled out.
Therefore, we investigated the relationship between prenatal SHS
exposure and AD across various groups and the effects of sensitization
in a prospective birth cohort study. Additionally, we aimed to validate
our findings by determining the relationship between urine cotinine
levels during pregnancy and AD.